Photons-atoms interactions [Archive]

Kumar

Nov7-04, 07:44 AM

<jabberwocky><div class="vbmenu_control"><a href="jabberwocky:;" onClick="newWindow=window.open('','usenetCode','toolbar=no, location=no,scrollbars=yes,resizable=yes,status=no ,width=650,height=400'); newWindow.document.write('<HTML><HEAD><TITLE>Usenet ASCII</TITLE></HEAD><BODY topmargin=0 leftmargin=0 BGCOLOR=#F1F1F1><table border=0 width=625><td bgcolor=midnightblue><font color=#F1F1F1>This Usenet message\'s original ASCII form: </font></td></tr><tr><td width=449><br><br><font face=courier><UL><PRE>\n\nHello,\n\nI want to know about Photons-atoms interactions as under:-\n\n1. Whether emitted photons from any atom will be exactly similar &\nwith same energy as of absorbed photons?\n\n2. Can atoms remain excited for long? I mean if atoms absorb any\nphoton, can it remain excited for long with out emitting photon?\n\n3. If any substance, say stone piece, is divided into two pieces &\nthose two pieces are kept as some distance seprately. In consideration\nof \'energy is to be corresponded for photon-atom interactions, If one\npiece of stone is excited or vibrated--will it effect 2nd piece of\nthat stone kept at some distance?\n\nBest wishes.\n</UL></PRE></font></td></tr></table></BODY><HTML>');"> <IMG SRC=/images/buttons/ip.gif BORDER=0 ALIGN=CENTER ALT="View this Usenet post in original ASCII form">  View this Usenet post in original ASCII form </a></div><P></jabberwocky>Hello,

I want to know about Photons-atoms interactions as under:-

1. Whether emitted photons from any atom will be exactly similar &
with same energy as of absorbed photons?

2. Can atoms remain excited for long? I mean if atoms absorb any
photon, can it remain excited for long with out emitting photon?

3. If any substance, say stone piece, is divided into two pieces &
those two pieces are kept as some distance seprately. In consideration
of 'energy is to be corresponded for photon-atom interactions, If one
piece of stone is excited or vibrated--will it effect 2nd piece of
that stone kept at some distance?

Best wishes.

Igor Khavkine

Nov9-04, 03:45 AM

<jabberwocky><div class="vbmenu_control"><a href="jabberwocky:;" onClick="newWindow=window.open('','usenetCode','toolbar=no, location=no,scrollbars=yes,resizable=yes,status=no ,width=650,height=400'); newWindow.document.write('<HTML><HEAD><TITLE>Usenet ASCII</TITLE></HEAD><BODY topmargin=0 leftmargin=0 BGCOLOR=#F1F1F1><table border=0 width=625><td bgcolor=midnightblue><font color=#F1F1F1>This Usenet message\'s original ASCII form: </font></td></tr><tr><td width=449><br><br><font face=courier><UL><PRE>\n\n\nOn Sun, 07 Nov 2004 13:44:56 +0000, Kumar wrote:\n\n> I want to know about Photons-atoms interactions as under:-\n>\n> 1. Whether emitted photons from any atom will be exactly similar & with\n> same energy as of absorbed photons?\n\nAny photon that can be absorbed can also be emitted. This is required for\nthe interaction Hamiltonian to be hermitian.\n\n> 2. Can atoms remain excited for long? I mean if atoms absorb any photon,\n> can it remain excited for long with out emitting photon?\n\nThis depends. If there is a large gap between the energy of the excited\nstate and the next lowest energy accessible state, atom will decay to a\nlower energy state pretty quickly: (Delta T) ~ hbar/(Delta E). If, on the\nother hand, there is a bunch of closely spaced energy levels, if the atom\nis excited into one of these states it may stay there for quite a while,\njust oscillating between the different energy levels near by. These are\ncalled metastable states.\n\n> 3. If any substance, say stone piece, is divided into two pieces & those\n> two pieces are kept as some distance seprately. In consideration of\n> \'energy is to be corresponded for photon-atom interactions, If one piece\n> of stone is excited or vibrated--will it effect 2nd piece of that stone\n> kept at some distance?\n\nElectromagnetic interaction between neutral macroscopic objects are\nusually negligible. If they are very far apart, they won\'t feel each\nother. If they are close enough, they will experience van der Vaals\nattractive forces. If they get even closer together, you have to consider\nthe atomic interactions between the surfaces more seriously.\n\nHope this helps.\n\nIgor\n</UL></PRE></font></td></tr></table></BODY><HTML>');"> <IMG SRC=/images/buttons/ip.gif BORDER=0 ALIGN=CENTER ALT="View this Usenet post in original ASCII form">  View this Usenet post in original ASCII form </a></div><P></jabberwocky>On Sun, 07 Nov 2004 13:44:56 +0000, Kumar wrote:

> I want to know about Photons-atoms interactions as under:-
>
> 1. Whether emitted photons from any atom will be exactly similar & with
> same energy as of absorbed photons?

Any photon that can be absorbed can also be emitted. This is required for
the interaction Hamiltonian to be hermitian.

> 2. Can atoms remain excited for long? I mean if atoms absorb any photon,
> can it remain excited for long with out emitting photon?

This depends. If there is a large gap between the energy of the excited
state and the next lowest energy accessible state, atom will decay to a
lower energy state pretty quickly: (\Delta T) ~ \hbar/(\Delta E). If, on the
other hand, there is a bunch of closely spaced energy levels, if the atom
is excited into one of these states it may stay there for quite a while,
just oscillating between the different energy levels near by. These are
called metastable states.

> 3. If any substance, say stone piece, is divided into two pieces & those
> two pieces are kept as some distance seprately. In consideration of
> 'energy is to be corresponded for photon-atom interactions, If one piece
> of stone is excited or vibrated--will it effect 2nd piece of that stone
> kept at some distance?

Electromagnetic interaction between neutral macroscopic objects are
usually negligible. If they are very far apart, they won't feel each
other. If they are close enough, they will experience van der Vaals
attractive forces. If they get even closer together, you have to consider
the atomic interactions between the surfaces more seriously.

Hope this helps.

Igor

Caroline Thompson

Nov9-04, 03:45 AM

<jabberwocky><div class="vbmenu_control"><a href="jabberwocky:;" onClick="newWindow=window.open('','usenetCode','toolbar=no, location=no,scrollbars=yes,resizable=yes,status=no ,width=650,height=400'); newWindow.document.write('<HTML><HEAD><TITLE>Usenet ASCII</TITLE></HEAD><BODY topmargin=0 leftmargin=0 BGCOLOR=#F1F1F1><table border=0 width=625><td bgcolor=midnightblue><font color=#F1F1F1>This Usenet message\'s original ASCII form: </font></td></tr><tr><td width=449><br><br><font face=courier><UL><PRE>\n\n\n"Kumar" <lordshiva5753@rediffmail.com> wrote in message\nnews:13b3b038.0411060248.11b30790@posting .google.com...\n\n> I want to know about Photons-atoms interactions as under:-\n>\n> 1. Whether emitted photons from any atom will be exactly\n> similar & with same energy as of absorbed photons?\n\nI\'ve been trying to find out facts on this. One source of information is:\n\nMössbauer, Rudolf L, "Recoilless nuclear resonance absorption of\ngamma radiation", Nobel Lecture, 1961,\nhttp://nobelprize.org/physics/laureates/1961/mossbauer-lecture.pdf,\n\nwhere I found that in resonance fluorescence of gamma rays with atomic\nnucleus there is expected to be a "line shift" due to recoil, the emitted\nlight being of very slightly longer wavelength. In other words, emitted\nlight is not always exactly the same frequency as that absorbed. The\nspecial feature of the Mossbauer effect is that the two frequencies *are*\nthe same.\n\n> 2. Can atoms remain excited for long? I mean if atoms absorb any\n> photon, can it remain excited for long with out emitting photon?\n\nI don\'t know. Schroedinger said:\n\n" ... the emitting system is busy all the time in producing the trains\nof light waves, it has no time left to tarry in the cherished \'stationary\nstates\', except perhaps in the ground state."\n(Quoted by Franco Selleri in "Quantum Paradoxes and Physical\nReality", A Van der Merwe, ed. (Kluwer Accademic, Dordrecht, 1990)\n\nIn "Wave Mechanics: Quantisation and proper values", Ann. D. Phys.\n79, (1926) Schroedinger expresses the idea that the emitted light that\nwe detect is really the beat corresponding to the difference between\ntwo higher frequencies:\n\n" . the frequency of the light is defined by the number of times per\nsecond the intensity maximum of the beat process repeats itself."\n\nCould it be that one of the frequencies is emitted all the time, but is at\ntoo high a frequency for us to detect? I should be very interested to know\nmore facts on this subject.\n\n> 3. If any substance, say stone piece, is divided into two pieces &\n> those two pieces are kept as some distance seprately. In consideration\n> of \'energy is to be corresponded for photon-atom interactions, If one\n> piece of stone is excited or vibrated--will it effect 2nd piece of\n> that stone kept at some distance?\n\nI think we can safely say "No" here.\n\nCaroline\n</UL></PRE></font></td></tr></table></BODY><HTML>');"> <IMG SRC=/images/buttons/ip.gif BORDER=0 ALIGN=CENTER ALT="View this Usenet post in original ASCII form">  View this Usenet post in original ASCII form </a></div><P></jabberwocky>"Kumar" <lordshiva5753@rediffmail.com> wrote in message
news:13b3b038.0411060248.11b30790@posting.google.c om...

> I want to know about Photons-atoms interactions as under:-
>
> 1. Whether emitted photons from any atom will be exactly
> similar & with same energy as of absorbed photons?

I've been trying to find out facts on this. One source of information is:

Mössbauer, Rudolf L, "Recoilless nuclear resonance absorption of
\gamma radiation", Nobel Lecture, 1961,
http://nobelprize.org/physics/laureates/1961/mossbauer-lecture.pdf,

where I found that in resonance fluorescence of \gamma rays with atomic
nucleus there is expected to be a "line shift" due to recoil, the emitted
light being of very slightly longer wavelength. In other words, emitted
light is not always exactly the same frequency as that absorbed. The
special feature of the Mossbauer effect is that the two frequencies *are*
the same.

> 2. Can atoms remain excited for long? I mean if atoms absorb any
> photon, can it remain excited for long with out emitting photon?

I don't know. Schroedinger said:

" ... the emitting system is busy all the time in producing the trains
of light waves, it has no time left to tarry in the cherished 'stationary
states', except perhaps in the ground state."
(Quoted by Franco Selleri in "Quantum Paradoxes and Physical
Reality", A Van der Merwe, ed. (Kluwer Accademic, Dordrecht, 1990)

In "Wave Mechanics: Quantisation and proper values", Ann. D. Phys.
79, (1926) Schroedinger expresses the idea that the emitted light that
we detect is really the beat corresponding to the difference between
two higher frequencies:

" . the frequency of the light is defined by the number of times per
second the intensity maximum of the beat process repeats itself."

Could it be that one of the frequencies is emitted all the time, but is at
too high a frequency for us to detect? I should be very interested to know
more facts on this subject.

> 3. If any substance, say stone piece, is divided into two pieces &
> those two pieces are kept as some distance seprately. In consideration
> of 'energy is to be corresponded for photon-atom interactions, If one
> piece of stone is excited or vibrated--will it effect 2nd piece of
> that stone kept at some distance?

I think we can safely say "No" here.

Caroline

Orcinus Orca

Nov9-04, 02:54 PM

<jabberwocky><div class="vbmenu_control"><a href="jabberwocky:;" onClick="newWindow=window.open('','usenetCode','toolbar=no, location=no,scrollbars=yes,resizable=yes,status=no ,width=650,height=400'); newWindow.document.write('<HTML><HEAD><TITLE>Usenet ASCII</TITLE></HEAD><BODY topmargin=0 leftmargin=0 BGCOLOR=#F1F1F1><table border=0 width=625><td bgcolor=midnightblue><font color=#F1F1F1>This Usenet message\'s original ASCII form: </font></td></tr><tr><td width=449><br><br><font face=courier><UL><PRE>lordshiva5753@rediffmail.com (Kumar) wrote in message news:<13b3b038.0411060248.11b30790@posting.google. com>...\n> Hello,\n>\n> I want to know about Photons-atoms interactions as under:-\n>\n> 1. Whether emitted photons from any atom will be exactly similar &\n> with same energy as of absorbed photons?\n\nLet me start by saying that I am a chemist so I may have\nmisinterpreted your question. For an atom to emit light, its outer\nelectrons have to be excited to higher energy orbitals, that is,\norbitals that are further away from the nucleus. One photon is not\nenough to excite an electron to a higher orbital. When atoms absorb\nlight, this light is given off as heat. If you manage to supply enough\nlight (energy) to excite an electron to the next orbital, when it goes\nback to its original orbital it will emit light and each element emits\nin a unique wavelength, never different. For example, if you get a\nspoon with kitchen salt and put it under a flame, the light emitted\nwill always be orange (sodium). Chemists use this fact to do chemical\nanalysis. The method is called Flame Emissive Spectrometry.\n\n> 2. Can atoms remain excited for long? I mean if atoms absorb any\n> photon, can it remain excited for long with out emitting photon?\n\nNo. It gets rid of the incoming energy by giving off heat. When atoms\nemit photons, they are getting rid of the incoming energy more\neffectively by allowing their electrons to keep bouncing back and\nforth from a lower orbital to a higher orbital. If the amount of\nenergy you supply is greater than the atom can disperse (e.g., x-ray),\nthen it will lose an electron (ionization) and react with nearby atoms\nto regain stability. This is why x-ray or ultraviolet light may cause\ncancer. It changes the structure of your DNA.\n\n> 3. If any substance, say stone piece, is divided into two pieces &\n> those two pieces are kept as some distance seprately. In consideration\n> of \'energy is to be corresponded for photon-atom interactions, If one\n> piece of stone is excited or vibrated--will it effect 2nd piece of\n> that stone kept at some distance?\n\nOnly if the energy source also reaches the second piece.\n\n</UL></PRE></font></td></tr></table></BODY><HTML>');"> <IMG SRC=/images/buttons/ip.gif BORDER=0 ALIGN=CENTER ALT="View this Usenet post in original ASCII form">  View this Usenet post in original ASCII form </a></div><P></jabberwocky>lordshiva5753@rediffmail.com (Kumar) wrote in message news:<13b3b038.0411060248.11b30790@posting.google.com>...
> Hello,
>
> I want to know about Photons-atoms interactions as under:-
>
> 1. Whether emitted photons from any atom will be exactly similar &
> with same energy as of absorbed photons?

Let me start by saying that I am a chemist so I may have
misinterpreted your question. For an atom to emit light, its outer
electrons have to be excited to higher energy orbitals, that is,
orbitals that are further away from the nucleus. One photon is not
enough to excite an electron to a higher orbital. When atoms absorb
light, this light is given off as heat. If you manage to supply enough
light (energy) to excite an electron to the next orbital, when it goes
back to its original orbital it will emit light and each element emits
in a unique wavelength, never different. For example, if you get a
spoon with kitchen salt and put it under a flame, the light emitted
will always be orange (sodium). Chemists use this fact to do chemical
analysis. The method is called Flame Emissive Spectrometry.

> 2. Can atoms remain excited for long? I mean if atoms absorb any
> photon, can it remain excited for long with out emitting photon?

No. It gets rid of the incoming energy by giving off heat. When atoms
emit photons, they are getting rid of the incoming energy more
effectively by allowing their electrons to keep bouncing back and
forth from a lower orbital to a higher orbital. If the amount of
energy you supply is greater than the atom can disperse (e.g., x-ray),
then it will lose an electron (ionization) and react with nearby atoms
to regain stability. This is why x-ray or ultraviolet light may cause
cancer. It changes the structure of your DNA.

> 3. If any substance, say stone piece, is divided into two pieces &
> those two pieces are kept as some distance seprately. In consideration
> of 'energy is to be corresponded for photon-atom interactions, If one
> piece of stone is excited or vibrated--will it effect 2nd piece of
> that stone kept at some distance?

Only if the energy source also reaches the second piece.

Kumar

Nov14-04, 11:59 AM

<jabberwocky><div class="vbmenu_control"><a href="jabberwocky:;" onClick="newWindow=window.open('','usenetCode','toolbar=no, location=no,scrollbars=yes,resizable=yes,status=no ,width=650,height=400'); newWindow.document.write('<HTML><HEAD><TITLE>Usenet ASCII</TITLE></HEAD><BODY topmargin=0 leftmargin=0 BGCOLOR=#F1F1F1><table border=0 width=625><td bgcolor=midnightblue><font color=#F1F1F1>This Usenet message\'s original ASCII form: </font></td></tr><tr><td width=449><br><br><font face=courier><UL><PRE>\n\n\n\n\norcinus_orca@hotpop.com (Orcinus Orca) wrote in message news:<87e684ba.0411120618.4644c20a@posting.google. com>...\n> lordshiva5753@rediffmail.com (Kumar) wrote in message\n>\n> > Thanks for nice reply. It appears from your reply that \'photons of any\n> > energy can be absorbed by any atom & more phtons may be required for\n> > orbital shift to next higher level. What will happen is some photons\n> > of lesser energy than minimum requred for orbital shift is absorbed?\n> > Will that atom keep/store this lesser energy & atom will remain some\n> > excited (metastable state as indicated)till it gets more energy?\n>\n> Kumar, something just occurred to me. By any chance, do you think that\n> everything you see is emitting light? For example, sunlight hits a\n> tree and you only see the tree because it absorbed some photons and\n> emits some back?\n>\n> Just about everything you see on earth is reflecting light, not\n> emitting light. If I remember my art classes correctly (this goes back\n> even further, to high school), white light is composed of light of\n> seven colors (the rainbow). The color you see on an object is the\n> color or colors the object is reflecting. The other colors\n> (wavelengths) were absorbed and "transformed" into heat. A red car\n> reflects red light and absorbs all other colors. This is why white\n> cars are "cooler" than black cars. Black absorbs all colors while\n> white reflects all colors. Things on Earth that emit light are: light\n> bulbs, flash lights, flashes, flames, electrical short circuits,\n> things that are extremely hot (lava, molten metal), lightning, etc\n> (everything you can see in the dark without a light source).\n> Everything else is just reflecting light.\n\nDear orcinus_orca,\n\nThanks for reply. Frankly, I am trying to know that whether atoms can\nabsorb some energy & remain some excied for long time without emission\nof photons. In physics this is called "metastable state" i.e. energy\nlevels in between two energy levels. But people says this stage can\'t\nexist for long(even for a second). But I doubt it in logical thinking.\nYou see when we stretch a spring or place a stone on hill, these\nstore/trap some potential energy & this can exist for any time till we\nbring themto their origional position. People define it that it is\njust a change in position, but I think atoms of spring or stone should\nbe in some excited state, otherwise how we can show potencial energy\nstored in the same.\n\nYou have indicated one important thought in your above reply. When we\nhit white light to any substance say tree as you said. Tree absorb\nall wavelength & reflect green wavelengths. It means tree absorb\nphotons of all wave lengths but reflect only photons of same green\nwavelength. It proves that atoms can absorb differant wavelengths\ncombined or differant energies but will always emit same energy level\nphoton.\n\n\nHowever, we have to find out that whether atoms can trap/store some\nenergy for long time or not? What atoms of tree do with other\nwavelengths than green wavelength? If it is lost as heat, how it\nradiate/emit heat?\n</UL></PRE></font></td></tr></table></BODY><HTML>');"> <IMG SRC=/images/buttons/ip.gif BORDER=0 ALIGN=CENTER ALT="View this Usenet post in original ASCII form">  View this Usenet post in original ASCII form </a></div><P></jabberwocky>orcinus_orca@hotpop.com (Orcinus Orca) wrote in message news:<87e684ba.0411120618.4644c20a@posting.google.com>...
> lordshiva5753@rediffmail.com (Kumar) wrote in message
>
> > Thanks for nice reply. It appears from your reply that 'photons of any
> > energy can be absorbed by any atom & more phtons may be required for
> > orbital shift to next higher level. What will happen is some photons
> > of lesser energy than minimum requred for orbital shift is absorbed?
> > Will that atom keep/store this lesser energy & atom will remain some
> > excited (metastable state as indicated)till it gets more energy?
>
> Kumar, something just occurred to me. By any chance, do you think that
> everything you see is emitting light? For example, sunlight hits a
> tree and you only see the tree because it absorbed some photons and
> emits some back?
>
> Just about everything you see on earth is reflecting light, not
> emitting light. If I remember my art classes correctly (this goes back
> even further, to high school), white light is composed of light of
> seven colors (the rainbow). The color you see on an object is the
> color or colors the object is reflecting. The other colors
> (wavelengths) were absorbed and "transformed" into heat. A red car
> reflects red light and absorbs all other colors. This is why white
> cars are "cooler" than black cars. Black absorbs all colors while
> white reflects all colors. Things on Earth that emit light are: light
> bulbs, flash lights, flashes, flames, electrical short circuits,
> things that are extremely hot (lava, molten metal), lightning, etc
> (everything you can see in the dark without a light source).
> Everything else is just reflecting light.

Dear orcinus_orca,

Thanks for reply. Frankly, I am trying to know that whether atoms can
absorb some energy & remain some excied for long time without emission
of photons. In physics this is called "metastable state" i.e. energy
levels in between two energy levels. But people says this stage can't
exist for long(even for a second). But I doubt it in logical thinking.
You see when we stretch a spring or place a stone on hill, these
store/trap some potential energy & this can exist for any time till we
bring themto their origional position. People define it that it is
just a change in position, but I think atoms of spring or stone should
be in some excited state, otherwise how we can show potencial energy
stored in the same.

You have indicated one important thought in your above reply. When we
hit white light to any substance say tree as you said. Tree absorb
all wavelength & reflect green wavelengths. It means tree absorb
photons of all wave lengths but reflect only photons of same green
wavelength. It proves that atoms can absorb differant wavelengths
combined or differant energies but will always emit same energy level
photon.

However, we have to find out that whether atoms can trap/store some
energy for long time or not? What atoms of tree do with other
wavelengths than green wavelength? If it is lost as heat, how it
radiate/emit heat?

Igor Khavkine

Nov14-04, 11:59 AM

<jabberwocky><div class="vbmenu_control"><a href="jabberwocky:;" onClick="newWindow=window.open('','usenetCode','toolbar=no, location=no,scrollbars=yes,resizable=yes,status=no ,width=650,height=400'); newWindow.document.write('<HTML><HEAD><TITLE>Usenet ASCII</TITLE></HEAD><BODY topmargin=0 leftmargin=0 BGCOLOR=#F1F1F1><table border=0 width=625><td bgcolor=midnightblue><font color=#F1F1F1>This Usenet message\'s original ASCII form: </font></td></tr><tr><td width=449><br><br><font face=courier><UL><PRE>On Fri, 12 Nov 2004 19:11:03 +0000, Orcinus Orca wrote:\n\n> lordshiva5753@rediffmail.com (Kumar) wrote in message\n>\n>> Thanks for nice reply.\n>\n> No problem! :)\n>\n>> It appears from your reply that \'photons of any energy can be absorbed\n>> by any atom & more phtons may be required for orbital shift to next\n>> higher level.\n>\n> Yep, photons of any energy can be absorbed, reflected, or simply travel\n> through atoms (providing they don=C2=B4t hit the nucleus). I=C2=B4m no =\nexpert but\n> I understand that a substance that is transparent does not absorb or\n> reflect photons to any significant degree.\n\nYou can think macroscopic objects as very large quantum systems (which\nthey obviously are) with many many separate energy states which are very\nvery closely spaced (perhaps even infinitesimally closely). Taking into\naccount the discussion elsewhere in this thread, it\'s easy to see that the\nemission and absorption spectra of these objects will not be quantized as\nin the case of a simple atom. Instead they may contain continuous bands\nand may also contain gaps between them.\n\nAn object that is not transparent contains energy levels whose spacing\ncorresponds to wavelengths of visible light. While an object that is\ntransparent contains no energy levels whose spacing corresponds to visible\nlight. In other words, visible frequencies lie in a gap in the absorption\nspectrum of that material.\n\nFor example, the elementary excitations in metals are electrons and\nlattice vibrations. Their energies can be changed by an arbitrarily small\namount, that is why metals tend not to be transparent at lower\nfrequencies. The elementary excitations in glass, on the other hand, have\na minimum energy that separates them from the ground state, and if this\nminimum energy is greater than the energy of visible photons, the glass\ntends to be transparent at those frequencies.\n\nIgor\n\n</UL></PRE></font></td></tr></table></BODY><HTML>');"> <IMG SRC=/images/buttons/ip.gif BORDER=0 ALIGN=CENTER ALT="View this Usenet post in original ASCII form">  View this Usenet post in original ASCII form </a></div><P></jabberwocky>On Fri, 12 Nov 2004 19:11:03 +0000, Orcinus Orca wrote:

> lordshiva5753@rediffmail.com (Kumar) wrote in message
>
>> Thanks for nice reply.
>
> No problem! :)
>
>> It appears from your reply that 'photons of any energy can be absorbed
>> by any atom & more phtons may be required for orbital shift to next
>> higher level.
>
> Yep, photons of any energy can be absorbed, reflected, or simply travel
> through atoms (providing they don=C2=B4t hit the nucleus). I=C2=B4m no =
expert but
> I understand that a substance that is transparent does not absorb or
> reflect photons to any significant degree.

You can think macroscopic objects as very large quantum systems (which
they obviously are) with many many separate energy states which are very
very closely spaced (perhaps even infinitesimally closely). Taking into
account the discussion elsewhere in this thread, it's easy to see that the
emission and absorption spectra of these objects will not be quantized as
in the case of a simple atom. Instead they may contain continuous bands
and may also contain gaps between them.

An object that is not transparent contains energy levels whose spacing
corresponds to wavelengths of visible light. While an object that is
transparent contains no energy levels whose spacing corresponds to visible
light. In other words, visible frequencies lie in a gap in the absorption
spectrum of that material.

For example, the elementary excitations in metals are electrons and
lattice vibrations. Their energies can be changed by an arbitrarily small
amount, that is why metals tend not to be transparent at lower
frequencies. The elementary excitations in glass, on the other hand, have
a minimum energy that separates them from the ground state, and if this
minimum energy is greater than the energy of visible photons, the glass
tends to be transparent at those frequencies.

Igor

Igor Khavkine

Nov14-04, 11:59 AM

<jabberwocky><div class="vbmenu_control"><a href="jabberwocky:;" onClick="newWindow=window.open('','usenetCode','toolbar=no, location=no,scrollbars=yes,resizable=yes,status=no ,width=650,height=400'); newWindow.document.write('<HTML><HEAD><TITLE>Usenet ASCII</TITLE></HEAD><BODY topmargin=0 leftmargin=0 BGCOLOR=#F1F1F1><table border=0 width=625><td bgcolor=midnightblue><font color=#F1F1F1>This Usenet message\'s original ASCII form: </font></td></tr><tr><td width=449><br><br><font face=courier><UL><PRE>\nOn Fri, 12 Nov 2004 19:09:22 +0000, Kumar wrote:\n\n> Caroline,\n>\n> Thanks for reply. Other posters have informed that "metastable state" is\n> possible. This indicate that absorbed & emitted energy can be differant\n> from each other, but emitted energy will normally always be the same or\n> its wavelength will always be same.Also, atoms can be kept in excited\n> state for long. I can\'t say for sure, but these metastable states can\n> somewhat represent "potential energy" or trapped/resting energy. What are\n> your comments?\n\nIt is very easy for an atom to emit a photon that is of different\nfrequency than what it absorbed. Consider the Hydrogen spectrum. It is\ngiven by photon energies of the form (1/n^2 - 1/m^2) Ry, where Ry is the\nRydberg energy scale. Hydrogen atomic states are labeled by an integer n,\nand their energies are Ry/n^2. So when an electron jumps from one atomic\nstate to another, we see a photon emitted whose frequency is part of the\nHydrogen spectrum. If, to see a photon resulting from a jump from level n\nto level m, we had to excite the Hydrogen atom with a photon of exactly\nthe same frequency, then spectroscopy experiments would have been\nimpossible! Some frequencies of light can only be obtained as emission\nfrom certain transitions of certain atoms.\n\nHere\'s a caricature of what\'s going on\n\nExcited state\nwith energy E1\n----------------\n^ | Photon of energy E1-E2\n| | ~~~~~~~~~~~~~~>\nPhoton | |\n~~~~~~~> | | Excited state\nenergy E1 | V with energy E2\n| ----------------------\n|\n|\n| Ground state\n---------------------------------\n\nOf course, the electron will not stay in the state E2 very long either.\nSome time later it may emit a photon to go to yet a lower excited state,\nor to go back to the ground state directly. There are many different ways\nfor an excited atom to get rid of some energy, and the probabilities of\nthese different processes can be calculated.\n\nIgor\n</UL></PRE></font></td></tr></table></BODY><HTML>');"> <IMG SRC=/images/buttons/ip.gif BORDER=0 ALIGN=CENTER ALT="View this Usenet post in original ASCII form">  View this Usenet post in original ASCII form </a></div><P></jabberwocky>On Fri, 12 Nov 2004 19:09:22 +0000, Kumar wrote:

> Caroline,
>
> Thanks for reply. Other posters have informed that "metastable state" is
> possible. This indicate that absorbed & emitted energy can be differant
> from each other, but emitted energy will normally always be the same or
> its wavelength will always be same.Also, atoms can be kept in excited
> state for long. I can't say for sure, but these metastable states can
> somewhat represent "potential energy" or trapped/resting energy. What are
> your comments?

It is very easy for an atom to emit a photon that is of different
frequency than what it absorbed. Consider the Hydrogen spectrum. It is
given by photon energies of the form (1/n^2 - 1/m^2) Ry, where Ry is the
Rydberg energy scale. Hydrogen atomic states are labeled by an integer n,
and their energies are Ry/n^2. So when an electron jumps from one atomic
state to another, we see a photon emitted whose frequency is part of the
Hydrogen spectrum. If, to see a photon resulting from a jump from level n
to level m, we had to excite the Hydrogen atom with a photon of exactly
the same frequency, then spectroscopy experiments would have been
impossible! Some frequencies of light can only be obtained as emission
from certain transitions of certain atoms.

Here's a caricature of what's going on

Excited state
with energy E1
----------------
^ | Photon of energy E1-E2| | ~~~~~~~~~~~~~~>
Photon | |
~~~~~~~> | | Excited state
energy E1 | V with energy E2
| ----------------------
|
|
| Ground state
---------------------------------

Of course, the electron will not stay in the state E2 very long either.
Some time later it may emit a photon to go to yet a lower excited state,
or to go back to the ground state directly. There are many different ways
for an excited atom to get rid of some energy, and the probabilities of
these different processes can be calculated.

Igor

Caroline Thompson

Nov14-04, 11:59 AM

<jabberwocky><div class="vbmenu_control"><a href="jabberwocky:;" onClick="newWindow=window.open('','usenetCode','toolbar=no, location=no,scrollbars=yes,resizable=yes,status=no ,width=650,height=400'); newWindow.document.write('<HTML><HEAD><TITLE>Usenet ASCII</TITLE></HEAD><BODY topmargin=0 leftmargin=0 BGCOLOR=#F1F1F1><table border=0 width=625><td bgcolor=midnightblue><font color=#F1F1F1>This Usenet message\'s original ASCII form: </font></td></tr><tr><td width=449><br><br><font face=courier><UL><PRE>\n\n\n\n"Kumar" <lordshiva5753@rediffmail.com> wrote in message\nnews:13b3b038.0411100323.39bc6d16@posting .google.com...\n> "Caroline Thompson" <ch.thompson1@virgin.net> wrote in message\n> news:<uEujd.484\\$127.293@newsfe2-gui.ntli.net>...\n\n>> > 1. Whether emitted photons from any atom will be exactly\n>> > similar & with same energy as of absorbed photons?\n>>\n>> I\'ve been trying to find out facts on this. One source of information is:\n>>\n>> Mössbauer, Rudolf L, "Recoilless nuclear resonance absorption of\n>> gamma radiation", Nobel Lecture, 1961,\n>> http://nobelprize.org/physics/laureates/1961/mossbauer-lecture.pdf,\n\n[snip]\n\n>> > 2. Can atoms remain excited for long? I mean if atoms absorb any\n>> > photon, can it remain excited for long with out emitting photon?\n>>\n>> I don\'t know. Schroedinger said:\n>>\n>> " ... the emitting system is busy all the time in producing the trains\n>> of light waves, it has no time left to tarry in the cherished \'stationary\n>> states\', except perhaps in the ground state."\n>> (Quoted by Franco Selleri in "Quantum Paradoxes and Physical\n>> Reality", A Van der Merwe, ed. (Kluwer Accademic, Dordrecht, 1990)\n>>\n>> In "Wave Mechanics: Quantisation and proper values", Ann. D. Phys.\n>> 79, (1926) Schroedinger expresses the idea that the emitted light that\n>> we detect is really the beat corresponding to the difference between\n>> two higher frequencies:\n>>\n>> " . the frequency of the light is defined by the number of times per\n>> second the intensity maximum of the beat process repeats itself."\n>>\n>> Could it be that one of the frequencies is emitted all the time, but is\n>> at\n>> too high a frequency for us to detect? I should be very interested to\n>> know\n>> more facts on this subject.\n\n[snip]\n\n> Thanks for reply. Other posters have informed that "metastable state"\n> is possible. This indicate that absorbed & emitted energy can be\n> differant from each other, but emitted energy will normally always be\n> the same or its wavelength will always be same.\n\nThe Moessbauer work suggests that the emitted wavelength will more often be\nslightly longer, so I don\'t know what to believe.\n\n> Also, atoms can be kept in excited state for long.\n\nCertain kinds of laser can emit continuous waves that are coherent over long\nperiods. In my view this must have a classical explanation. Something must\nbe oscillating continuously, so the emitted light here cannot be due to\nelectrons jumping between energy states. Atoms in magneto-optical traps\nseem able to emit over long periods too. See for instance\nhttp://physics.nist.gov/Divisions/Div841/Gp3/Projects/Atom/cr_atoms_proj.html\n\n> I can\'t say for sure, but these metastable states can somewhat\n> represent "potential energy" or trapped/resting\n> energy. What are your comments?\n\nThat sounds plausible, but it\'s hard to know the truth in a world in which\nall energy is *assumed* to come in units of hf.\n\nCaroline\n\nCaroline H Thompson\n\nch.thompson1@virgin.net\nhttp://freespace.virgin.net/ch.thompson1/\n\n</UL></PRE></font></td></tr></table></BODY><HTML>');"> <IMG SRC=/images/buttons/ip.gif BORDER=0 ALIGN=CENTER ALT="View this Usenet post in original ASCII form">  View this Usenet post in original ASCII form </a></div><P></jabberwocky>"Kumar" <lordshiva5753@rediffmail.com> wrote in message
news:13b3b038.0411100323.39bc6d16@posting.google.c om...
> "Caroline Thompson" <ch.thompson1@virgin.net> wrote in message
> news:<uEujd.484$127.293@newsfe2-gui.ntli.net>...

>> > 1. Whether emitted photons from any atom will be exactly
>> > similar & with same energy as of absorbed photons?
>>
>> I've been trying to find out facts on this. One source of information is:
>>
>> Mössbauer, Rudolf L, "Recoilless nuclear resonance absorption of
>> \gamma radiation", Nobel Lecture, 1961,
>> http://nobelprize.org/physics/laureates/1961/mossbauer-lecture.pdf,

[snip]

>> > 2. Can atoms remain excited for long? I mean if atoms absorb any
>> > photon, can it remain excited for long with out emitting photon?
>>
>> I don't know. Schroedinger said:
>>
>> " ... the emitting system is busy all the time in producing the trains
>> of light waves, it has no time left to tarry in the cherished 'stationary
>> states', except perhaps in the ground state."
>> (Quoted by Franco Selleri in "Quantum Paradoxes and Physical
>> Reality", A Van der Merwe, ed. (Kluwer Accademic, Dordrecht, 1990)
>>
>> In "Wave Mechanics: Quantisation and proper values", Ann. D. Phys.
>> 79, (1926) Schroedinger expresses the idea that the emitted light that
>> we detect is really the beat corresponding to the difference between
>> two higher frequencies:
>>
>> " . the frequency of the light is defined by the number of times per
>> second the intensity maximum of the beat process repeats itself."
>>
>> Could it be that one of the frequencies is emitted all the time, but is
>> at
>> too high a frequency for us to detect? I should be very interested to
>> know
>> more facts on this subject.

[snip]

> Thanks for reply. Other posters have informed that "metastable state"
> is possible. This indicate that absorbed & emitted energy can be
> differant from each other, but emitted energy will normally always be
> the same or its wavelength will always be same.

The Moessbauer work suggests that the emitted wavelength will more often be
slightly longer, so I don't know what to believe.

> Also, atoms can be kept in excited state for long.

Certain kinds of laser can emit continuous waves that are coherent over long
periods. In my view this must have a classical explanation. Something must
be oscillating continuously, so the emitted light here cannot be due to
electrons jumping between energy states. Atoms in magneto-optical traps
seem able to emit over long periods too. See for instance
http://physics.nist.gov/Divisions/Div841/Gp3/Projects/Atom/cr_atoms_proj.html

> I can't say for sure, but these metastable states can somewhat
> represent "potential energy" or trapped/resting
> energy. What are your comments?

That sounds plausible, but it's hard to know the truth in a world in which
all energy is *assumed* to come in units of hf.

Caroline

Caroline H Thompson

ch.thompson1@virgin.net
http://freespace.virgin.net/ch.thompson1/

Orcinus Orca

Nov16-04, 02:56 AM

<jabberwocky><div class="vbmenu_control"><a href="jabberwocky:;" onClick="newWindow=window.open('','usenetCode','toolbar=no, location=no,scrollbars=yes,resizable=yes,status=no ,width=650,height=400'); newWindow.document.write('<HTML><HEAD><TITLE>Usenet ASCII</TITLE></HEAD><BODY topmargin=0 leftmargin=0 BGCOLOR=#F1F1F1><table border=0 width=625><td bgcolor=midnightblue><font color=#F1F1F1>This Usenet message\'s original ASCII form: </font></td></tr><tr><td width=449><br><br><font face=courier><UL><PRE>\n\n"Caroline Thompson" <ch.thompson1@virgin.net> wrote in message\n\n> Certain kinds of laser can emit continuous waves that are coherent over long\n> periods. In my view this must have a classical explanation. Something must\n> be oscillating continuously, so the emitted light here cannot be due to\n> electrons jumping between energy states. Atoms in magneto-optical traps\n> seem able to emit over long periods too. See for instance\n> http://physics.nist.gov/Divisions/Div841/Gp3/Projects/Atom/cr_atoms_proj.html\n> Caroline H Thompson\n\nLasers work in the same way: electrons "jumping up and down." There\nare some minor differences such as the number of excited atoms at any\ngiven time and how the laser parts are assembled.\nCheck out http://science.howstuffworks.com/laser.htm\nOr see more Google results on how lasers work:\nhttp://www.google.com/search?hl=en&q=%27how+lasers+work%27\n</UL></PRE></font></td></tr></table></BODY><HTML>');"> <IMG SRC=/images/buttons/ip.gif BORDER=0 ALIGN=CENTER ALT="View this Usenet post in original ASCII form">  View this Usenet post in original ASCII form </a></div><P></jabberwocky>"Caroline Thompson" <ch.thompson1@virgin.net> wrote in message

> Certain kinds of laser can emit continuous waves that are coherent over long
> periods. In my view this must have a classical explanation. Something must
> be oscillating continuously, so the emitted light here cannot be due to
> electrons jumping between energy states. Atoms in magneto-optical traps
> seem able to emit over long periods too. See for instance
> http://physics.nist.gov/Divisions/Div841/Gp3/Projects/Atom/cr_atoms_proj.html
> Caroline H Thompson

Lasers work in the same way: electrons "jumping up and down." There
are some minor differences such as the number of excited atoms at any
given time and how the laser parts are assembled.
Check out http://science.howstuffworks.com/laser.htm
Or see more Google results on how lasers work:
http://www.google.com/search?hl=en&q=%27how+lasers+work%27

Orcinus Orca

Nov16-04, 02:56 AM

<jabberwocky><div class="vbmenu_control"><a href="jabberwocky:;" onClick="newWindow=window.open('','usenetCode','toolbar=no, location=no,scrollbars=yes,resizable=yes,status=no ,width=650,height=400'); newWindow.document.write('<HTML><HEAD><TITLE>Usenet ASCII</TITLE></HEAD><BODY topmargin=0 leftmargin=0 BGCOLOR=#F1F1F1><table border=0 width=625><td bgcolor=midnightblue><font color=#F1F1F1>This Usenet message\'s original ASCII form: </font></td></tr><tr><td width=449><br><br><font face=courier><UL><PRE>\n\nlordshiva5753@rediffmail.com (Kumar) wrote in message\n> Thanks for reply. Frankly, I am trying to know that whether atoms can\n> absorb some energy & remain some excied for long time without emission\n> of photons.\n\nYes they can. I just learned it yesterday. There are compounds called\nphosphors that manage to stay in excited states for quite a long time\n(hours). One example of a phosphor is zinc sulfide. An electron is\nexcited by photons to a higher energy level and suffers a change in\nspin. It gets trapped in this higher energy orbital and cannot go back\nto the ground state. When this electron manages to absorb some heat\n(from the surroundings), it climbs to an even higher energy orbital\nand from this orbital it can go back to its ground state, emitting a\nphoton. This is how glow-in-the-dark toys work.\n\n> However, we have to find out that whether atoms can trap/store some\n> energy for long time or not?\n\nYes, phosphors can - they have the so called \'metastable state\'. You\ncan learn more if you do a search on phosphors or phosphorescence.\n\n> What atoms of tree do with other\n> wavelengths than green wavelength?\n\nPart of the photons absorbed is used for photosynthesis; the rest is\nlost vaporizing water (see below).\n\n> If it is lost as heat, how it\n> radiate/emit heat?\n\nPlants do not become hot despite sitting on the sun all day because\nthey sweat just like we do – it\'s called transpiration. The energy (in\nthis case, heat) is used up to make water go from the liquid state\ninside plant to the gaseous state out to the atmosphere. A stone on\nthe other hand will become very hot because it does not transpire. Its\nheat is lost to the environment (air and ground).\n</UL></PRE></font></td></tr></table></BODY><HTML>');"> <IMG SRC=/images/buttons/ip.gif BORDER=0 ALIGN=CENTER ALT="View this Usenet post in original ASCII form">  View this Usenet post in original ASCII form </a></div><P></jabberwocky>lordshiva5753@rediffmail.com (Kumar) wrote in message
> Thanks for reply. Frankly, I am trying to know that whether atoms can
> absorb some energy & remain some excied for long time without emission
> of photons.

Yes they can. I just learned it yesterday. There are compounds called
phosphors that manage to stay in excited states for quite a long time
(hours). One example of a phosphor is zinc sulfide. An electron is
excited by photons to a higher energy level and suffers a change in
spin. It gets trapped in this higher energy orbital and cannot go back
to the ground state. When this electron manages to absorb some heat
(from the surroundings), it climbs to an even higher energy orbital
and from this orbital it can go back to its ground state, emitting a
photon. This is how glow-in-the-dark toys work.

> However, we have to find out that whether atoms can trap/store some
> energy for long time or not?

Yes, phosphors can - they have the so called 'metastable state'. You
can learn more if you do a search on phosphors or phosphorescence.

> What atoms of tree do with other
> wavelengths than green wavelength?

Part of the photons absorbed is used for photosynthesis; the rest is
lost vaporizing water (see below).

> If it is lost as heat, how it
> radiate/emit heat?

Plants do not become hot despite sitting on the sun all day because
they sweat just like we do – it's called transpiration. The energy (in
this case, heat) is used up to make water go from the liquid state
inside plant to the gaseous state out to the atmosphere. A stone on
the other hand will become very hot because it does not transpire. Its
heat is lost to the environment (air and ground).

Kumar

Nov16-04, 02:56 AM

<jabberwocky><div class="vbmenu_control"><a href="jabberwocky:;" onClick="newWindow=window.open('','usenetCode','toolbar=no, location=no,scrollbars=yes,resizable=yes,status=no ,width=650,height=400'); newWindow.document.write('<HTML><HEAD><TITLE>Usenet ASCII</TITLE></HEAD><BODY topmargin=0 leftmargin=0 BGCOLOR=#F1F1F1><table border=0 width=625><td bgcolor=midnightblue><font color=#F1F1F1>This Usenet message\'s original ASCII form: </font></td></tr><tr><td width=449><br><br><font face=courier><UL><PRE>\n\nIgor Khavkine <k_igor_k@lycos.com> wrote in message news:<pan.2004.11.13.00.56.43.144164@lycos.com>... \n> On Fri, 12 Nov 2004 19:09:22 +0000, Kumar wrote:\n>\n> > Caroline,\n> >\n> > Thanks for reply. Other posters have informed that "metastable state" is\n> > possible. This indicate that absorbed & emitted energy can be differant\n> > from each other, but emitted energy will normally always be the same or\n> > its wavelength will always be same.Also, atoms can be kept in excited\n> > state for long. I can\'t say for sure, but these metastable states can\n> > somewhat represent "potential energy" or trapped/resting energy. What are\n> > your comments?\n>\n> It is very easy for an atom to emit a photon that is of different\n> frequency than what it absorbed. Consider the Hydrogen spectrum. It is\n> given by photon energies of the form (1/n^2 - 1/m^2) Ry, where Ry is the\n> Rydberg energy scale. Hydrogen atomic states are labeled by an integer n,\n> and their energies are Ry/n^2. So when an electron jumps from one atomic\n> state to another, we see a photon emitted whose frequency is part of the\n> Hydrogen spectrum. If, to see a photon resulting from a jump from level n\n> to level m, we had to excite the Hydrogen atom with a photon of exactly\n> the same frequency, then spectroscopy experiments would have been\n> impossible! Some frequencies of light can only be obtained as emission\n> from certain transitions of certain atoms.\n>\n> Here\'s a caricature of what\'s going on\n>\n> Excited state\n> with energy E1\n> ----------------\n> ^ | Photon of energy E1-E2\n> | | ~~~~~~~~~~~~~~>\n> Photon | |\n> ~~~~~~~> | | Excited state\n> energy E1 | V with energy E2\n> | ----------------------\n> |\n> |\n> | Ground state\n> ---------------------------------\n>\n> Of course, the electron will not stay in the state E2 very long either.\n> Some time later it may emit a photon to go to yet a lower excited state,\n> or to go back to the ground state directly. There are many different ways\n> for an excited atom to get rid of some energy, and the probabilities of\n> these different processes can be calculated.\n>\n> Igor\n\nIgor, Thanks for nice explaination. But what about metastable states.\nSuppose an atom is excited in between Ground state & E1 state(if it is\npossible & provided E1 level is first next shell than the ground\nstate). It can\'t emit photon specific to that atom. How then this atom\nwill get rid of this extra absorbed energy?\n\nIs it so that; absorbed energy which do not match with the emission\nlevels as specific photon to that atom is relesed as Mechnical\nwaves(sound)>>Heat>>(photons if more energy is added)?\n</UL></PRE></font></td></tr></table></BODY><HTML>');"> <IMG SRC=/images/buttons/ip.gif BORDER=0 ALIGN=CENTER ALT="View this Usenet post in original ASCII form">  View this Usenet post in original ASCII form </a></div><P></jabberwocky>Igor Khavkine <k_{igor_k}@lycos.com> wrote in message news:<pan.2004.11.13.00.56.43.144164@lycos.com>...
> On Fri, 12 Nov 2004 19:09:22 +0000, Kumar wrote:
>
> > Caroline,
> >
> > Thanks for reply. Other posters have informed that "metastable state" is
> > possible. This indicate that absorbed & emitted energy can be differant
> > from each other, but emitted energy will normally always be the same or
> > its wavelength will always be same.Also, atoms can be kept in excited
> > state for long. I can't say for sure, but these metastable states can
> > somewhat represent "potential energy" or trapped/resting energy. What are
> > your comments?
>
> It is very easy for an atom to emit a photon that is of different
> frequency than what it absorbed. Consider the Hydrogen spectrum. It is
> given by photon energies of the form (1/n^2 - 1/m^2) Ry, where Ry is the
> Rydberg energy scale. Hydrogen atomic states are labeled by an integer n,
> and their energies are Ry/n^2. So when an electron jumps from one atomic
> state to another, we see a photon emitted whose frequency is part of the
> Hydrogen spectrum. If, to see a photon resulting from a jump from level n
> to level m, we had to excite the Hydrogen atom with a photon of exactly
> the same frequency, then spectroscopy experiments would have been
> impossible! Some frequencies of light can only be obtained as emission
> from certain transitions of certain atoms.
>
> Here's a caricature of what's going on
>
> Excited state
> with energy E1
> ----------------
> ^ | Photon of energy E1-E2
> | | ~~~~~~~~~~~~~~>
> Photon | |
> ~~~~~~~> | | Excited state
> energy E1 | V with energy E2
> | ----------------------
> |
> |
> | Ground state
> ---------------------------------
>
> Of course, the electron will not stay in the state E2 very long either.
> Some time later it may emit a photon to go to yet a lower excited state,
> or to go back to the ground state directly. There are many different ways
> for an excited atom to get rid of some energy, and the probabilities of
> these different processes can be calculated.
>
> Igor

Igor, Thanks for nice explaination. But what about metastable states.
Suppose an atom is excited in between Ground state & E1 state(if it is
possible & provided E1 level is first next shell than the ground
state). It can't emit photon specific to that atom. How then this atom
will get rid of this extra absorbed energy?

Is it so that; absorbed energy which do not match with the emission
levels as specific photon to that atom is relesed as Mechnical
waves(sound)>>Heat>>(photons if more energy is added)?

Igor Khavkine

Nov17-04, 10:51 AM

<jabberwocky><div class="vbmenu_control"><a href="jabberwocky:;" onClick="newWindow=window.open('','usenetCode','toolbar=no, location=no,scrollbars=yes,resizable=yes,status=no ,width=650,height=400'); newWindow.document.write('<HTML><HEAD><TITLE>Usenet ASCII</TITLE></HEAD><BODY topmargin=0 leftmargin=0 BGCOLOR=#F1F1F1><table border=0 width=625><td bgcolor=midnightblue><font color=#F1F1F1>This Usenet message\'s original ASCII form: </font></td></tr><tr><td width=449><br><br><font face=courier><UL><PRE>On Tue, 16 Nov 2004 08:56:44 +0000, Kumar wrote:\n\n>\n>\n> Igor Khavkine <k_igor_k@lycos.com> wrote in message\n> news:<pan.2004.11.13.00.56.43.144164@lycos.com>... \n>> On Fri, 12 Nov 2004 19:09:22 +0000, Kumar wrote:\n>>\n>> > Caroline,\n>> >\n>> > Thanks for reply. Other posters have informed that "metastable state"\n>> > is possible. This indicate that absorbed & emitted energy can be\n>> > differant from each other, but emitted energy will normally always be\n>> > the same or its wavelength will always be same.Also, atoms can be kept\n>> > in excited state for long. I can\'t say for sure, but these metastable\n>> > states can somewhat represent "potential energy" or trapped/resting\n>> > energy. What are your comments?\n>>\n>> It is very easy for an atom to emit a photon that is of different\n>> frequency than what it absorbed. Consider the Hydrogen spectrum. It is\n>> given by photon energies of the form (1/n^2 - 1/m^2) Ry, where Ry is the\n>> Rydberg energy scale. Hydrogen atomic states are labeled by an integer\n>> n, and their energies are Ry/n^2. So when an electron jumps from one\n>> atomic state to another, we see a photon emitted whose frequency is part\n>> of the Hydrogen spectrum. If, to see a photon resulting from a jump from\n>> level n to level m, we had to excite the Hydrogen atom with a photon of\n>> exactly the same frequency, then spectroscopy experiments would have\n>> been impossible! Some frequencies of light can only be obtained as\n>> emission from certain transitions of certain atoms.\n>>\n>> Here\'s a caricature of what\'s going on\n>>\n>> Excited state\n>> with energy E1\n>> ----------------\n>> ^ | Photon of energy E1-E2\n>> | | ~~~~~~~~~~~~~~>\n>> Photon | |\n>> ~~~~~~~> | | Excited state energy E1\n>> | V with energy E2\n>> | ----------------------\n>> |\n>> |\n>> | Ground state\n>> ---------------------------------\n>>\n>> Of course, the electron will not stay in the state E2 very long either.\n>> Some time later it may emit a photon to go to yet a lower excited state,\n>> or to go back to the ground state directly. There are many different\n>> ways for an excited atom to get rid of some energy, and the\n>> probabilities of these different processes can be calculated.\n\n> Igor, Thanks for nice explaination. But what about metastable states.\n> Suppose an atom is excited in between Ground state & E1 state(if it is\n> possible & provided E1 level is first next shell than the ground state).\n> It can\'t emit photon specific to that atom. How then this atom will get\n> rid of this extra absorbed energy?\n\nThere is no actual state, in the same sense as the ground state and the E1\nstate, with definite energy strictly between the ground state and E1.\nHowever the atom can be in a superposition of several states with definite\nenergy and have have an average energy in between. I\'ve gone into some of\nthe details in another post in this thread. However, this superposition\nwould not be metastable as you expect. When coupled to the electromagnetic\nfield, the atom does not like to be in a superposition of states of very\ndifferent energies, so this superposition would be rather short lived.\n\nA metastable state is possible when the atom has several energy states\nwhich are very closely spaced, like so:\n\n============================== ^ dE, dE << E\n============================== | Many closely spaced levels\n============================== V of energy ~ E\n^\n|\n|\n| E\n|\n|\nV\n------------------------------ Ground State\n\nA metastable state would correspond to a superposition of some states\nwith energies close to E. The average energy of this state will be E, and\nit will be fairly long lived, on the order of hbar/dE time.\n\n> Is it so that; absorbed energy which do not match with the emission\n> levels as specific photon to that atom is relesed as Mechnical\n> waves(sound)>>Heat>>(photons if more energy is added)?\n\nIt is hard to think about sound and heat when talking of a single atom,\nsince those are collective phenomena. What you are wondering about is\nstill possible. An atom can store energy in its internal electronic states\nas well as in its total kinetic energy. So it is possible for it to absorb\na photon of a given energy, emit another photon with less energy, and\nconvert the deficit into kinetic energy. For a free electron this is\ncalled the Compton effect, but this effect holds for any particle that\ninteracts with the electromagnetic field. Here\'s an illustration:\n\nabsorbed emitted\nphoton of photon of\nenergy E1 energy E2\n~~~~~~~>~~~~~~------------------~~~~~~~>~~~~~~~~\n/ `.\nincoming / `. outgoing electron\nelectron / `. with extra kinetic\n/ `. energy of E1-E2\n/ `.\n/ `.\n\nIf you really want you could think of the extra kinetic energy going into\nsound or heat since these are just macroscopic consequences of the motion\nof individual atoms and molecules.\n\nHope this helps.\n\nIgor\n\n</UL></PRE></font></td></tr></table></BODY><HTML>');"> <IMG SRC=/images/buttons/ip.gif BORDER=0 ALIGN=CENTER ALT="View this Usenet post in original ASCII form">  View this Usenet post in original ASCII form </a></div><P></jabberwocky>On Tue, 16 Nov 2004 08:56:44 +0000, Kumar wrote:

>
>
> Igor Khavkine <k_{igor_k}@lycos.com> wrote in message
> news:<pan.2004.11.13.00.56.43.144164@lycos.com>...
>> On Fri, 12 Nov 2004 19:09:22 +0000, Kumar wrote:
>>
>> > Caroline,
>> >
>> > Thanks for reply. Other posters have informed that "metastable state"
>> > is possible. This indicate that absorbed & emitted energy can be
>> > differant from each other, but emitted energy will normally always be
>> > the same or its wavelength will always be same.Also, atoms can be kept
>> > in excited state for long. I can't say for sure, but these metastable
>> > states can somewhat represent "potential energy" or trapped/resting
>> > energy. What are your comments?
>>
>> It is very easy for an atom to emit a photon that is of different
>> frequency than what it absorbed. Consider the Hydrogen spectrum. It is
>> given by photon energies of the form (1/n^2 - 1/m^2) Ry, where Ry is the
>> Rydberg energy scale. Hydrogen atomic states are labeled by an integer
>> n, and their energies are Ry/n^2. So when an electron jumps from one
>> atomic state to another, we see a photon emitted whose frequency is part
>> of the Hydrogen spectrum. If, to see a photon resulting from a jump from
>> level n to level m, we had to excite the Hydrogen atom with a photon of
>> exactly the same frequency, then spectroscopy experiments would have
>> been impossible! Some frequencies of light can only be obtained as
>> emission from certain transitions of certain atoms.
>>
>> Here's a caricature of what's going on
>>
>> Excited state
>> with energy E1
>> ----------------
>> ^ | Photon of energy E1-E2>> | | ~~~~~~~~~~~~~~>
>> Photon | |
>> ~~~~~~~> | | Excited state energy E1
>> | V with energy E2
>> | ----------------------
>> |
>> |>> | Ground state
>> ---------------------------------
>>
>> Of course, the electron will not stay in the state E2 very long either.
>> Some time later it may emit a photon to go to yet a lower excited state,
>> or to go back to the ground state directly. There are many different
>> ways for an excited atom to get rid of some energy, and the
>> probabilities of these different processes can be calculated.

> Igor, Thanks for nice explaination. But what about metastable states.
> Suppose an atom is excited in between Ground state & E1 state(if it is
> possible & provided E1 level is first next shell than the ground state).
> It can't emit photon specific to that atom. How then this atom will get
> rid of this extra absorbed energy?

There is no actual state, in the same sense as the ground state and the E1
state, with definite energy strictly between the ground state and E1.
However the atom can be in a superposition of several states with definite
energy and have have an average energy in between. I've gone into some of
the details in another post in this thread. However, this superposition
would not be metastable as you expect. When coupled to the electromagnetic
field, the atom does not like to be in a superposition of states of very
different energies, so this superposition would be rather short lived.

A metastable state is possible when the atom has several energy states
which are very closely spaced, like so:

============================== ^ dE, dE << E
============================== | Many closely spaced levels
============================== V of energy ~ E
^
|
|
| E
|
|
V
------------------------------ Ground State

A metastable state would correspond to a superposition of some states
with energies close to E. The average energy of this state will be E, and
it will be fairly long lived, on the order of \hbar/dE time.

> Is it so that; absorbed energy which do not match with the emission
> levels as specific photon to that atom is relesed as Mechnical
> waves(sound)>>Heat>>(photons if more energy is added)?

It is hard to think about sound and heat when talking of a single atom,
since those are collective phenomena. What you are wondering about is
still possible. An atom can store energy in its internal electronic states
as well as in its total kinetic energy. So it is possible for it to absorb
a photon of a given energy, emit another photon with less energy, and
convert the deficit into kinetic energy. For a free electron this is
called the Compton effect, but this effect holds for any particle that
interacts with the electromagnetic field. Here's an illustration:

absorbed emitted
photon of photon of
energy E1 energy E2
~~~~~~~>~~~~~~------------------~~~~~~~>~~~~~~~~
/ `.
incoming / `. outgoing electron
electron / `. with extra kinetic
/ `. energy of E1-E2
/ `.
/ `.

If you really want you could think of the extra kinetic energy going into
sound or heat since these are just macroscopic consequences of the motion
of individual atoms and molecules.

Hope this helps.

Igor

Caroline Thompson

Nov17-04, 10:51 AM

<jabberwocky><div class="vbmenu_control"><a href="jabberwocky:;" onClick="newWindow=window.open('','usenetCode','toolbar=no, location=no,scrollbars=yes,resizable=yes,status=no ,width=650,height=400'); newWindow.document.write('<HTML><HEAD><TITLE>Usenet ASCII</TITLE></HEAD><BODY topmargin=0 leftmargin=0 BGCOLOR=#F1F1F1><table border=0 width=625><td bgcolor=midnightblue><font color=#F1F1F1>This Usenet message\'s original ASCII form: </font></td></tr><tr><td width=449><br><br><font face=courier><UL><PRE>"Orcinus Orca" <orcinus_orca@hotpop.com> wrote in message\nnews:87e684ba.0411141613.724e42af@posting .google.com...\n>\n> "Caroline Thompson" <ch.thompson1@virgin.net> wrote\n>\n>> Certain kinds of laser can emit continuous waves that are\n>> coherent over long periods. In my view this must have\n>> a classical explanation. Something must be oscillating\n>> continuously, so the emitted light here cannot be due to\n>> electrons jumping between energy states ...\n>\n> Lasers work in the same way: electrons "jumping up and down."\n> There are some minor differences such as the number of excited\n> atoms at any given time and how the laser parts are assembled.\n> Check out http://science.howstuffworks.com/laser.htm\n> Or see more Google results on how lasers work:\n> http://www.google.com/search?hl=en&q=%27how+lasers+work%27\n\nThanks, but I still think there are simpler explanations waiting to be\nfound, and these involve continuous oscillations. The first "masers", I\'ve\nheard (from Azimov\'s "Science") were thought of in terms of atoms\noscillating within molecules. I don\'t see why lasers should be that\ndifferent. There are oscillators that get stimulated by continuous waves.\n\nCaroline\n\nch.thompson1@virgin.net\nhtt p://freespace.virgin.net/ch.thompson1/\n\n</UL></PRE></font></td></tr></table></BODY><HTML>');"> <IMG SRC=/images/buttons/ip.gif BORDER=0 ALIGN=CENTER ALT="View this Usenet post in original ASCII form">  View this Usenet post in original ASCII form </a></div><P></jabberwocky>"Orcinus Orca" <orcinus_orca@hotpop.com> wrote in message
news:87e684ba.0411141613.724e42af@posting.google.c om...
>
> "Caroline Thompson" <ch.thompson1@virgin.net> wrote
>
>> Certain kinds of laser can emit continuous waves that are
>> coherent over long periods. In my view this must have
>> a classical explanation. Something must be oscillating
>> continuously, so the emitted light here cannot be due to
>> electrons jumping between energy states ...
>
> Lasers work in the same way: electrons "jumping up and down."
> There are some minor differences such as the number of excited
> atoms at any given time and how the laser parts are assembled.
> Check out http://science.howstuffworks.com/laser.htm
> Or see more Google results on how lasers work:
> http://www.google.com/search?hl=en&q=%27how+lasers+work%27

Thanks, but I still think there are simpler explanations waiting to be
found, and these involve continuous oscillations. The first "masers", I've
heard (from Azimov's "Science") were thought of in terms of atoms
oscillating within molecules. I don't see why lasers should be that
different. There are oscillators that get stimulated by continuous waves.

Caroline

ch.thompson1@virgin.net
http://freespace.virgin.net/ch.thompson1/

Kumar

Nov18-04, 12:52 PM

<jabberwocky><div class="vbmenu_control"><a href="jabberwocky:;" onClick="newWindow=window.open('','usenetCode','toolbar=no, location=no,scrollbars=yes,resizable=yes,status=no ,width=650,height=400'); newWindow.document.write('<HTML><HEAD><TITLE>Usenet ASCII</TITLE></HEAD><BODY topmargin=0 leftmargin=0 BGCOLOR=#F1F1F1><table border=0 width=625><td bgcolor=midnightblue><font color=#F1F1F1>This Usenet message\'s original ASCII form: </font></td></tr><tr><td width=449><br><br><font face=courier><UL><PRE>\norcinus_orca@hotpop.com (Orcinus Orca) wrote in message news:<87e684ba.0411141611.25f4b8b0@posting.google. com>...\n> lordshiva5753@rediffmail.com (Kumar) wrote in message\n> > Thanks for reply. Frankly, I am trying to know that whether atoms can\n> > absorb some energy & remain some excied for long time without emission\n> > of photons.\n>\n> Yes they can. I just learned it yesterday. There are compounds called\n> phosphors that manage to stay in excited states for quite a long time\n> (hours). One example of a phosphor is zinc sulfide. An electron is\n> excited by photons to a higher energy level and suffers a change in\n> spin. It gets trapped in this higher energy orbital and cannot go back\n> to the ground state. When this electron manages to absorb some heat\n> (from the surroundings), it climbs to an even higher energy orbital\n> and from this orbital it can go back to its ground state, emitting a\n> photon. This is how glow-in-the-dark toys work.\n>\n> > However, we have to find out that whether atoms can trap/store some\n> > energy for long time or not?\n>\n> Yes, phosphors can - they have the so called \'metastable state\'. You\n> can learn more if you do a search on phosphors or phosphorescence.\n>\n> > What atoms of tree do with other\n> > wavelengths than green wavelength?\n>\n> Part of the photons absorbed is used for photosynthesis; the rest is\n> lost vaporizing water (see below).\n>\n> > If it is lost as heat, how it\n> > radiate/emit heat?\n>\n> Plants do not become hot despite sitting on the sun all day because\n> they sweat just like we do ? it\'s called transpiration. The energy (in\n> this case, heat) is used up to make water go from the liquid state\n> inside plant to the gaseous state out to the atmosphere. A stone on\n> the other hand will become very hot because it does not transpire. Its\n> heat is lost to the environment (air and ground).\n\norcinus_orca,\n\nThanks. Now let us look at prism, it can absorb white light & emit\nseveral wave lengths. Water can also create prism effect. Black colour\ncan also absorb several wavelengths. I want to know that atoms with\nlower atomic numbers OR Carbon, Hydrogen & Oxygen as in water, alcohol\nor sugar have some broad spectrum/several wavelengths absorbing\nproperties?\n</UL></PRE></font></td></tr></table></BODY><HTML>');"> <IMG SRC=/images/buttons/ip.gif BORDER=0 ALIGN=CENTER ALT="View this Usenet post in original ASCII form">  View this Usenet post in original ASCII form </a></div><P></jabberwocky>orcinus_orca@hotpop.com (Orcinus Orca) wrote in message news:<87e684ba.0411141611.25f4b8b0@posting.google.com>...
> lordshiva5753@rediffmail.com (Kumar) wrote in message
> > Thanks for reply. Frankly, I am trying to know that whether atoms can
> > absorb some energy & remain some excied for long time without emission
> > of photons.
>
> Yes they can. I just learned it yesterday. There are compounds called
> phosphors that manage to stay in excited states for quite a long time
> (hours). One example of a phosphor is zinc sulfide. An electron is
> excited by photons to a higher energy level and suffers a change in
> spin. It gets trapped in this higher energy orbital and cannot go back
> to the ground state. When this electron manages to absorb some heat
> (from the surroundings), it climbs to an even higher energy orbital
> and from this orbital it can go back to its ground state, emitting a
> photon. This is how glow-in-the-dark toys work.
>
> > However, we have to find out that whether atoms can trap/store some
> > energy for long time or not?
>
> Yes, phosphors can - they have the so called 'metastable state'. You
> can learn more if you do a search on phosphors or phosphorescence.
>
> > What atoms of tree do with other
> > wavelengths than green wavelength?
>
> Part of the photons absorbed is used for photosynthesis; the rest is
> lost vaporizing water (see below).
>
> > If it is lost as heat, how it
> > radiate/emit heat?
>
> Plants do not become hot despite sitting on the sun all day because
> they sweat just like we do ? it's called transpiration. The energy (in
> this case, heat) is used up to make water go from the liquid state
> inside plant to the gaseous state out to the atmosphere. A stone on
> the other hand will become very hot because it does not transpire. Its
> heat is lost to the environment (air and ground).

orcinus_orca,

Thanks. Now let us look at prism, it can absorb white light & emit
several wave lengths. Water can also create prism effect. Black colour
can also absorb several wavelengths. I want to know that atoms with
lower atomic numbers OR Carbon, Hydrogen & Oxygen as in water, alcohol
or sugar have some broad spectrum/several wavelengths absorbing
properties?

Igor Khavkine

Nov19-04, 12:07 PM

<jabberwocky><div class="vbmenu_control"><a href="jabberwocky:;" onClick="newWindow=window.open('','usenetCode','toolbar=no, location=no,scrollbars=yes,resizable=yes,status=no ,width=650,height=400'); newWindow.document.write('<HTML><HEAD><TITLE>Usenet ASCII</TITLE></HEAD><BODY topmargin=0 leftmargin=0 BGCOLOR=#F1F1F1><table border=0 width=625><td bgcolor=midnightblue><font color=#F1F1F1>This Usenet message\'s original ASCII form: </font></td></tr><tr><td width=449><br><br><font face=courier><UL><PRE>\nOn Thu, 18 Nov 2004 18:52:52 +0000, Kumar wrote:\n\n> Thanks. Now let us look at prism, it can absorb white light & emit\n> several wave lengths. Water can also create prism effect. Black colour\n> can also absorb several wavelengths. I want to know that atoms with\n> lower atomic numbers OR Carbon, Hydrogen & Oxygen as in water, alcohol\n> or sugar have some broad spectrum/several wavelengths absorbing\n> properties?\n\nThat is not what happens in a prism, at least that is not the source of\nthe main effect. The white light that comes into a prism is already\ncomposed of a number of different frequencies. The rays for different\nfrequencies travel differently inside the prism, that is why the come out\nseparated.\n\nYou can think of this effect classically where the medium (the prism)\nabsorbs nothing but possesses a refractive index that bends the path or a\nlight ray. Or if you really want to bring in quantum mechanics you can\nthink of the photons in the white bean bouncing off the atoms in a certain\nway but not changing frequency. You could also think of the atoms\nabsorbing the photons then very quickly re-emitting them in different\ndirections without changing the frequency. However you should be weary of\nthe word "absorption" in this context. See my post about short time\ndynamics of photon-atom interactions for details.\n\nAtoms (and gasses of them) usually have line absorption spectra since they\nhave discrete energy levels. Macroscopic samples usually have broad\nabsorption bands since they often have continua of excitation.\n\nIgor\n\n</UL></PRE></font></td></tr></table></BODY><HTML>');"> <IMG SRC=/images/buttons/ip.gif BORDER=0 ALIGN=CENTER ALT="View this Usenet post in original ASCII form">  View this Usenet post in original ASCII form </a></div><P></jabberwocky>On Thu, 18 Nov 2004 18:52:52 +0000, Kumar wrote:

> Thanks. Now let us look at prism, it can absorb white light & emit
> several wave lengths. Water can also create prism effect. Black colour
> can also absorb several wavelengths. I want to know that atoms with
> lower atomic numbers OR Carbon, Hydrogen & Oxygen as in water, alcohol
> or sugar have some broad spectrum/several wavelengths absorbing
> properties?

That is not what happens in a prism, at least that is not the source of
the main effect. The white light that comes into a prism is already
composed of a number of different frequencies. The rays for different
frequencies travel differently inside the prism, that is why the come out
separated.

You can think of this effect classically where the medium (the prism)
absorbs nothing but possesses a refractive index that bends the path or a
light ray. Or if you really want to bring in quantum mechanics you can
think of the photons in the white bean bouncing off the atoms in a certain
way but not changing frequency. You could also think of the atoms
absorbing the photons then very quickly re-emitting them in different
directions without changing the frequency. However you should be weary of
the word "absorption" in this context. See my post about short time
dynamics of photon-atom interactions for details.

Atoms (and gasses of them) usually have line absorption spectra since they
have discrete energy levels. Macroscopic samples usually have broad
absorption bands since they often have continua of excitation.

Igor

Oz

Nov19-04, 01:28 PM

<jabberwocky><div class="vbmenu_control"><a href="jabberwocky:;" onClick="newWindow=window.open('','usenetCode','toolbar=no, location=no,scrollbars=yes,resizable=yes,status=no ,width=650,height=400'); newWindow.document.write('<HTML><HEAD><TITLE>Usenet ASCII</TITLE></HEAD><BODY topmargin=0 leftmargin=0 BGCOLOR=#F1F1F1><table border=0 width=625><td bgcolor=midnightblue><font color=#F1F1F1>This Usenet message\'s original ASCII form: </font></td></tr><tr><td width=449><br><br><font face=courier><UL><PRE>Kumar <lordshiva5753@rediffmail.com> writes\n\n>However, we have to find out that whether atoms can trap/store some\n>energy for long time or not? What atoms of tree do with other\n>wavelengths than green wavelength? If it is lost as heat, how it\n>radiate/emit heat?\n\nAtoms are tricky little things that tend to do things rather quickly.\n\nMolecules are more interesting, and they certainly can hold energy for\nextended periods. One only needs to consider fluorescence or even more\nextreme phosphorescence to see that.\n\nObtainable from your local toys department....\n\n--\nOz\nThis post is worth absolutely nothing and is probably fallacious.\n\nUse oz@farmeroz.port995.com [ozacoohdb@despammed.com functions].\nBTOPENWORLD address has ceased. DEMON address has ceased.\n\n</UL></PRE></font></td></tr></table></BODY><HTML>');"> <IMG SRC=/images/buttons/ip.gif BORDER=0 ALIGN=CENTER ALT="View this Usenet post in original ASCII form">  View this Usenet post in original ASCII form </a></div><P></jabberwocky>Kumar <lordshiva5753@rediffmail.com> writes

>However, we have to find out that whether atoms can trap/store some
>energy for long time or not? What atoms of tree do with other
>wavelengths than green wavelength? If it is lost as heat, how it
>radiate/emit heat?

Atoms are tricky little things that tend to do things rather quickly.

Molecules are more interesting, and they certainly can hold energy for
extended periods. One only needs to consider fluorescence or even more
extreme phosphorescence to see that.

Obtainable from your local toys department....

--
Oz
This post is worth absolutely nothing and is probably fallacious.

Use oz@farmeroz.port995.com [ozacoohdb@despammed.com functions].
BTOPENWORLD address has ceased. DEMON address has ceased.

Orcinus Orca

Nov19-04, 01:31 PM

<jabberwocky><div class="vbmenu_control"><a href="jabberwocky:;" onClick="newWindow=window.open('','usenetCode','toolbar=no, location=no,scrollbars=yes,resizable=yes,status=no ,width=650,height=400'); newWindow.document.write('<HTML><HEAD><TITLE>Usenet ASCII</TITLE></HEAD><BODY topmargin=0 leftmargin=0 BGCOLOR=#F1F1F1><table border=0 width=625><td bgcolor=midnightblue><font color=#F1F1F1>This Usenet message\'s original ASCII form: </font></td></tr><tr><td width=449><br><br><font face=courier><UL><PRE>lordshiva5753@rediffmail.com (Kumar) wrote in message\n> Thanks. Now let us look at prism, it can absorb white light & emit\n> several wave lengths. Water can also create prism effect. Black colour\n> can also absorb several wavelengths. I want to know that atoms with\n> lower atomic numbers OR Carbon, Hydrogen & Oxygen as in water, alcohol\n> or sugar have some broad spectrum/several wavelengths absorbing\n> properties?\n\nPrisms and water droplets are not emitting light when you see a\nrainbow, they are *refracting* light. Please take a look at\nhttp://science.howstuffworks.com/question41.htm\n\n</UL></PRE></font></td></tr></table></BODY><HTML>');"> <IMG SRC=/images/buttons/ip.gif BORDER=0 ALIGN=CENTER ALT="View this Usenet post in original ASCII form">  View this Usenet post in original ASCII form </a></div><P></jabberwocky>lordshiva5753@rediffmail.com (Kumar) wrote in message
> Thanks. Now let us look at prism, it can absorb white light & emit
> several wave lengths. Water can also create prism effect. Black colour
> can also absorb several wavelengths. I want to know that atoms with
> lower atomic numbers OR Carbon, Hydrogen & Oxygen as in water, alcohol
> or sugar have some broad spectrum/several wavelengths absorbing
> properties?

Prisms and water droplets are not emitting light when you see a
rainbow, they are *refracting* light. Please take a look at
http://science.howstuffworks.com/question41.htm

Kumar

Nov21-04, 02:51 AM

<jabberwocky><div class="vbmenu_control"><a href="jabberwocky:;" onClick="newWindow=window.open('','usenetCode','toolbar=no, location=no,scrollbars=yes,resizable=yes,status=no ,width=650,height=400'); newWindow.document.write('<HTML><HEAD><TITLE>Usenet ASCII</TITLE></HEAD><BODY topmargin=0 leftmargin=0 BGCOLOR=#F1F1F1><table border=0 width=625><td bgcolor=midnightblue><font color=#F1F1F1>This Usenet message\'s original ASCII form: </font></td></tr><tr><td width=449><br><br><font face=courier><UL><PRE>Igor Khavkine <k_igor_k@lycos.com> wrote in message news:<pan.2004.11.19.05.32.29.174968@lycos.com>... \n> On Thu, 18 Nov 2004 18:52:52 +0000, Kumar wrote:\n>\n> > Thanks. Now let us look at prism, it can absorb white light & emit\n> > several wave lengths. Water can also create prism effect. Black colour\n> > can also absorb several wavelengths. I want to know that atoms with\n> > lower atomic numbers OR Carbon, Hydrogen & Oxygen as in water, alcohol\n> > or sugar have some broad spectrum/several wavelengths absorbing\n> > properties?\n>\n> That is not what happens in a prism, at least that is not the source of\n> the main effect. The white light that comes into a prism is already\n> composed of a number of different frequencies. The rays for different\n> frequencies travel differently inside the prism, that is why the come out\n> separated.\n>\n> You can think of this effect classically where the medium (the prism)\n> absorbs nothing but possesses a refractive index that bends the path or a\n> light ray. Or if you really want to bring in quantum mechanics you can\n> think of the photons in the white bean bouncing off the atoms in a certain\n> way but not changing frequency. You could also think of the atoms\n> absorbing the photons then very quickly re-emitting them in different\n> directions without changing the frequency. However you should be weary of\n> the word "absorption" in this context. See my post about short time\n> dynamics of photon-atom interactions for details.\n>\n> Atoms (and gasses of them) usually have line absorption spectra since they\n> have discrete energy levels. Macroscopic samples usually have broad\n> absorption bands since they often have continua of excitation.\n>\n> Igor\n\nThanks. I consider prism effect as \'the atoms\nabsorbing the photons then very quickly re-emitting them in different\ndirections without changing the frequency. Btw, whether slowing down\nof differant lights composed in white light at differant speeds, is\nthere or not in case of prism effect?\n\n</UL></PRE></font></td></tr></table></BODY><HTML>');"> <IMG SRC=/images/buttons/ip.gif BORDER=0 ALIGN=CENTER ALT="View this Usenet post in original ASCII form">  View this Usenet post in original ASCII form </a></div><P></jabberwocky>Igor Khavkine <k_{igor_k}@lycos.com> wrote in message news:<pan.2004.11.19.05.32.29.174968@lycos.com>...
> On Thu, 18 Nov 2004 18:52:52 +0000, Kumar wrote:
>
> > Thanks. Now let us look at prism, it can absorb white light & emit
> > several wave lengths. Water can also create prism effect. Black colour
> > can also absorb several wavelengths. I want to know that atoms with
> > lower atomic numbers OR Carbon, Hydrogen & Oxygen as in water, alcohol
> > or sugar have some broad spectrum/several wavelengths absorbing
> > properties?
>
> That is not what happens in a prism, at least that is not the source of
> the main effect. The white light that comes into a prism is already
> composed of a number of different frequencies. The rays for different
> frequencies travel differently inside the prism, that is why the come out
> separated.
>
> You can think of this effect classically where the medium (the prism)
> absorbs nothing but possesses a refractive index that bends the path or a
> light ray. Or if you really want to bring in quantum mechanics you can
> think of the photons in the white bean bouncing off the atoms in a certain
> way but not changing frequency. You could also think of the atoms
> absorbing the photons then very quickly re-emitting them in different
> directions without changing the frequency. However you should be weary of
> the word "absorption" in this context. See my post about short time
> dynamics of photon-atom interactions for details.
>
> Atoms (and gasses of them) usually have line absorption spectra since they
> have discrete energy levels. Macroscopic samples usually have broad
> absorption bands since they often have continua of excitation.
>
> Igor

Thanks. I consider prism effect as 'the atoms
absorbing the photons then very quickly re-emitting them in different
directions without changing the frequency. Btw, whether slowing down
of differant lights composed in white light at differant speeds, is
there or not in case of prism effect?

Kumar

Nov22-04, 05:14 AM

<jabberwocky><div class="vbmenu_control"><a href="jabberwocky:;" onClick="newWindow=window.open('','usenetCode','toolbar=no, location=no,scrollbars=yes,resizable=yes,status=no ,width=650,height=400'); newWindow.document.write('<HTML><HEAD><TITLE>Usenet ASCII</TITLE></HEAD><BODY topmargin=0 leftmargin=0 BGCOLOR=#F1F1F1><table border=0 width=625><td bgcolor=midnightblue><font color=#F1F1F1>This Usenet message\'s original ASCII form: </font></td></tr><tr><td width=449><br><br><font face=courier><UL><PRE>\n\norcinus_orca@hotpop.com (Orcinus Orca) wrote in message news:<87e684ba.0411190151.2745251a@posting.google. com>...\n> lordshiva5753@rediffmail.com (Kumar) wrote in message\n> > Thanks. Now let us look at prism, it can absorb white light & emit\n> > several wave lengths. Water can also create prism effect. Black colour\n> > can also absorb several wavelengths. I want to know that atoms with\n> > lower atomic numbers OR Carbon, Hydrogen & Oxygen as in water, alcohol\n> > or sugar have some broad spectrum/several wavelengths absorbing\n> > properties?\n>\n> Prisms and water droplets are not emitting light when you see a\n> rainbow, they are *refracting* light. Please take a look at\n> http://science.howstuffworks.com/question41.htm\n\nI mean absorbing white light & emitting differant light due to\nrefraction or travel of differant lights at differant speed through a\nmedium or refraction which takes place for light passing from one\nmedium to another.\n</UL></PRE></font></td></tr></table></BODY><HTML>');"> <IMG SRC=/images/buttons/ip.gif BORDER=0 ALIGN=CENTER ALT="View this Usenet post in original ASCII form">  View this Usenet post in original ASCII form </a></div><P></jabberwocky>orcinus_orca@hotpop.com (Orcinus Orca) wrote in message news:<87e684ba.0411190151.2745251a@posting.google.com>...
> lordshiva5753@rediffmail.com (Kumar) wrote in message
> > Thanks. Now let us look at prism, it can absorb white light & emit
> > several wave lengths. Water can also create prism effect. Black colour
> > can also absorb several wavelengths. I want to know that atoms with
> > lower atomic numbers OR Carbon, Hydrogen & Oxygen as in water, alcohol
> > or sugar have some broad spectrum/several wavelengths absorbing
> > properties?
>
> Prisms and water droplets are not emitting light when you see a
> rainbow, they are *refracting* light. Please take a look at
> http://science.howstuffworks.com/question41.htm

I mean absorbing white light & emitting differant light due to
refraction or travel of differant lights at differant speed through a
medium or refraction which takes place for light passing from one
medium to another.