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Can spectrum be distorted?

  1. Jul 10, 2006 #1
    Hello,

    In our day to day life, we see objects from distance in same shape and colour. Sunlight also reaches to us in somewhat same spectrum as it is emitted from sun.

    As such, why spectrum, interfered by atmosphere, is not changed or distorted--normally?

    Whether emitted, reflected or transmitted spectrum allways persist--somewhat alike sprit of a substance?

    Best wishes.
     
  2. jcsd
  3. Jul 10, 2006 #2

    Danger

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    It's changed all of the time, kumar. Every time that there's a change in the refractive index that the light is going through, the spectrum is somewhat altered. That, after all, is why the sky is blue.
    It is also (immeasurably, perhaps), shifted according to whether you are moving toward or away from the sun.
     
  4. Jul 11, 2006 #3
    Still, how it remains grossly the same?
     
  5. Jul 11, 2006 #4

    Astronuc

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    As Danger indicated, the spectrum is changing all the time - particularly with different amounts of dust and clouds in the air. The orientation of any one place on the earth with respect to incident light from the sun changes constantly due to rotation of the earth, and this in turn changes the depth of atmosphere through which sunlight is transmitted. That's why the sun appears redder at sunset - blue light scatters more than red light.
     
  6. Jul 11, 2006 #5
    Still there is some persitency in spectrum lines of sunlight.

    Anyway, why we could see and recognize some object at distant place?
     
  7. Jul 11, 2006 #6

    Danger

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    I see... you mean the gross frequency content of the light. That's because the sun is a constant source. The same elements are providing the photons all of the time (primarily hydrogen and helium). Every element has its own characteristic emission/absorbtion lines, which don't vary over time. Astronomy would be in a sad state if that weren't true, because it's how we determine the composition of other stars, dust clouds, etc.. Spectrographic analysis of material here on Earth would also be impossible otherwise.
     
  8. Jul 11, 2006 #7
    Yes, but atmosphere will also be a constant source for interfearances.

    Moreover we can see any object similarily. How it can happen?
     
  9. Jul 11, 2006 #8

    DaveC426913

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    Light rays are very, very straight and very, very fast. It takes a lot of messing with them to distort them.

    The atmosphere bends light only a small bit. It is only noticeable over many miles of distance.

    Let me ask you something: have you looked at buidlings, trees or landscape from, say twenty miles distance?
    Are the colours the same intensity, or are they very faded?
    Are they still across the spectrum, or are distant objects mostly bluish?
    Is everything perfectly sharp, or is it fuzzy, indistinct and even a little wavy?
    If you look across tha large body of water, are objects at the horizon perfectly shaped are are they grossly distorted?
     
  10. Jul 11, 2006 #9

    chroot

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    I'd just like to point out that, while the atmosphere is mostly transparent to visible light, it is far from transparent to other wavelengths. Infrared, ultraviolet, X-rays, and other forms of electromagnetic radiation are all scattered or completely absorbed by our atmosphere.

    In fact, you could even make the argument that we evolved to use visible light for our sense of vision because it happened to be the band of wavelengths that "survive" the best in our atmosphere without much scattering or absorption.

    - Warren
     
  11. Jul 12, 2006 #10
    Then say in common, these are not effected grossly by interfering atmosphere and my pesist??

    Yes but that may be due to capacity of our eves We still can see clearly by help of lenses.
     
  12. Jul 12, 2006 #11
    chroot,In suh view. can we cnsider visible/reflected spectum can persist for long--may be wondering?
     
  13. Jul 12, 2006 #12

    DaveC426913

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    I didn't quite catch that. Say again?


    Nope. Try it. Look at the something very far away (10+ miles) through binoculars. It will be faded in colours, hazy blue-grey, very indistinct and possibly even wavy.
     
  14. Jul 12, 2006 #13
    I was watching a Bumble-Bee yesterday, while trying to get my head round calculus, in my conservatory. It was constantly trying to fly through the plexi-glass roof even though to me it was blatently not completley transparent. I thought to myself how it was odd that it didnt wise up and fly out the door it came in through, since they have the abillity to navigate so well why would they have trouble with the plastic?

    Well i came to the conclusion that it was most likley due to their inabillity to distinguish between the frequencies of light that pentrate the plastic. Therfor although the plastic is slightly opaque to me, to the bee it was transparent and no different from the sky.

    After all, i read somewhere that the bees eyes are more atuned to UV light and that the flowers have vivid colors in this light spectral range.

    I also chuckled and thought that i am blind to so many frequencies of EM and how strange it would be if i could see them all all the time. Then i wonder if there is a circumstance where i am like the bee, banging on some plexi-glass somewhere.

    Anyway, Just thought id share that as it seemed fitting.
     
    Last edited: Jul 12, 2006
  15. Jul 12, 2006 #14

    Danger

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    Good theory, 3. It would explain why my windows always end up full of bugs. I never thought of that possibility. I wonder if tinted windows would have the same effect.
     
  16. Jul 12, 2006 #15
     
  17. Jul 12, 2006 #16

    Gokul43201

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    It remains "grossly" the same because the medium of propagation of light is a low density gas. If our atmosphere were made of water, you'd really not be able to see things very well.

    PS : Please keep your questions clear and specific.
     
  18. Jul 12, 2006 #17

    Claude Bile

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    The OP may be enquiring as to why the spectral (absorption) lines, from say, the sun, don't shift in frequency as they pass through, say, our atmosphere.

    If so, then the answer is due to the linear response of the atoms and molecules to an applied EM field. To get the generation of new frequencies you need a nonlinear response.

    Does that answer your question kumar?

    Claude.
     
  19. Jul 12, 2006 #18
    But all constituents of environment are nor similar and persisting?

    Will it also happen similarily with emitted or reflected spectrums from earth to space?

    Gokul, sorry my first language was not english. However I shall try. Meantime pls accomadate.
     
  20. Jul 13, 2006 #19

    Astronuc

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    Adding to what Danger mentioned, the sun is like a black body radiator with an approximate temperature of about 5800 K, and therefore the sun's light (and spectrum) are fairly constant. The earth's atmosphere is fairly constant, except for clouds and perhaps dust blown into the air.

    See these articles about the sun -
    http://en.wikipedia.org/wiki/Sun
    http://en.wikipedia.org/wiki/Structure_of_the_Sun#Photosphere

    And about the visible spectrum -
    http://en.wikipedia.org/wiki/Optical_spectrum

    and particularly
    http://en.wikipedia.org/wiki/Image:Atmospheric_electromagnetic_transmittance_or_opacity.jpg

    The earth's atmosphere 'scatters' light and during the course of a day, the atmospheric conditions will change, and the scattered light will have the same spectrum, but with different intensities of particular frequencies (wavelengths). It is the intensity of the lines that changes.

    Adding to what Gokul mentioned, if one goes underwater, one sees a dramatic changed in the spectrum as one goes deeper. The blue and red light frequencies are absorbed quite readily and IIRC, the yellow frequencies are the most visible many meters underwater.
     
    Last edited: Jul 13, 2006
  21. Jul 13, 2006 #20

    DaveC426913

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    Because, literally, bees cannot "wise up".

    While it seems like they have some very sophisticated mechanisms for locating food and home, like all insects, their complex mechanisms are really composed of layers of very simple mechanisms.

    When in reduced light conditions, insects fly towards light. Period. They cannot stop this mechanism. If they manage to find their way into a place where the brightest light comes from one particular direction, they will fly toward it till doomsday. This is not a thinking process, it is more basic than that.

    I saw on a nature channel once, the explanation about why moths flutter around night lights. The amount of light that impacts their wings affects the flapping mechanism of the wings. If there is more light on the left wing than on the right wing, this causes the right wing to "speed up" and the left wing to "slow down" (ultra-simplification), resulting in a turn towards the light. There is no brain processing and no decision-making going on here at all.

    The roomba robot vacuum cleaner uses this level of logic. It doesn't think, it just has very simple mechanisms that will get it out of most jams.
    "If your forward sensors contact something, back up, turn a little, resume."
    95% of the time this kind of logic works great. 5% of the time it doesn't.

    Bees did not evolve in a world containing enclosed spaces with transparent rooves.

    The insects do have what may be one extra parameter to this mechanism: "add a random element to the length of turn or distance".
    With this extra element, the bumble bee may, after the 100th try, accidentally stumble upon the nearby-yet-lesser-lit open door - and escape.
     
    Last edited: Jul 13, 2006
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