B Absorption of electromagnetic radiation

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Hi, I wonder why with electromagnetic radiation, there's some radiation that penetrates with earth atmosphere such as visible light, while other can't like gamma radiation. What does the penetration of any em radiation on any object depends on
 
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Hi, I wonder why with electromagnetic radiation, there's some radiation that penetrates with earth atmosphere such as visible light, while other can't like gamma radiation. What does the penetration of any em radiation on any object depends on
It depends on the atomic constituents in the atmosphere.
On Earth we have a mostly nitrogen and oxygen atmosphere.
This permits most visible light, (and radio frequencies too), but is opaque to higher frequency EM.
It's opaque to higher frequency UV light, never mind gamma rays.
However gamma rays can be sufficiently energetic to break down ozone and other more rare gases.
 
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davenn

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davenn

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Hi, I wonder why with electromagnetic radiation, there's some radiation that penetrates with earth atmosphere such as visible light, while other can't like gamma radiation. What does the penetration of any em radiation on any object depends on
different wavelengths have varying amounts of absorption depending on the gasses and amounts of water vapour present

some links for you to read ......

https://astarmathsandphysics.com/a-level-physics-notes/electrons-and-photons/2669-transparency-of-atmosphere-to-electromagnetic-radiation.html

https://www.chegg.com/homework-help/definitions/atmospheric-em-transparency-2

http://gsp.humboldt.edu/OLM/Courses/GSP_216_Online/lesson2-1/atmosphere.html


Dave
 
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Yes. I meant that the more high frequency UV (UVC). which is the most likely to damage life, is mostly blocked.
Whereas UV closer to the visible spectrum (UVA) not blocked much, it is enough to get a sun tan.
UVA is even used in disco entertainment events!
 
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As explained in previous posts, how the atmospheric transmittance changes with wavelength depends on the chemical composition of the atmosphere.

I think it is interesting to realize that EM radiation in range 380-740 nm can be called visible light only because the Earth's atmosphere allows to transmit it (almost all without any strong absorption). As the solar radiation is most intense in approximately the same range of wavelengths, the evolution of living organisms is strongly influenced by this fact. Probably, a different part of spectrum would be called visible light, if the atmosphere had different chemical composition.
(if any intelligent beings had evolved under such conditions, of course)
 

sophiecentaur

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As explained in previous posts, how the atmospheric transmittance changes with wavelength depends on the chemical composition of the atmosphere.

I think it is interesting to realize that EM radiation in range 380-740 nm can be called visible light only because the Earth's atmosphere allows to transmit it (almost all without any strong absorption). As the solar radiation is most intense in approximately the same range of wavelengths, the evolution of living organisms is strongly influenced by this fact. Probably, a different part of spectrum would be called visible light, if the atmosphere had different chemical composition.
(if any intelligent beings had evolved under such conditions, of course)
That's evolution for you. We seldom developed abilities that wouldn't be advantageous to us. I find it a bit surprising that our sensitivity range doesn't actually include IR but I guess hominids didn't hunt at night when it could have been an advantage.
 
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The general reason why all substances strongly absorb UV radiation short of around 100 nm is the strength of electromagnetic binding between electrons and nuclei.
Hydrogen atoms are strongly absorbing blueward of Lyman alpha (121 nm). Most transparent of all substances is helium, which is strongly absorbing blueward of 60 nm.
While a few most stable and strongly bound atoms, molecules and solids are transparent to 100 nm, most common molecules and solids absorb also between 100...200 nm. Dioxygen absorbs blueward of 200 nm, dinitrogen blueward of 145 nm.
Living organisms are sensitive to UV because many of the more complex molecules essential to life contain even more weakly held electrons. Basically there are many organic molecules sensitive between 200 and 300 nm.
Further on...
How do we see?
Because eyes contain specialized complex molecules (retinal) that are specialized to absorb visible light reversibly and create sensation, while the light leaves intact the other complex molecules essential to light.
If retinal were sensitive to infrared, it would also be sensitive to infrared radiated by eye itself, or thermal movement of the retinal molecule directly causing the effect of absorbing IR. This is likely a reason that hampers development of infrared vision.
 

sophiecentaur

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@snorkack
All good points there. I was thinking that there are a number of animals* that 'see' UV and IR radiation but as you say, it would be hard to incorporate the extended frequency response into our regular vision systems. Not worth it for human / mammalian evolution, I guess.
*Snakes (at night) run cooler than mammals (which they predate) and insect multiple eyes are totally different from mammalian eyes so different technology involved.
 
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@snorkackAll good points there. I was thinking that there are a number of animals* that 'see' UV and IR radiation but as you say, it would be hard to incorporate the extended frequency response into our regular vision systems. Not worth it for human / mammalian evolution, I guess.
UV is fairly easy. Birds are close to mammals. Many species of birds can see ultraviolet. Many others cannot.
 
Hi, I wonder why with electromagnetic radiation, there's some radiation that penetrates with earth atmosphere such as visible light, while other can't like gamma radiation. What does the penetration of any em radiation on any object depends on
The object detecting the waves determine its viability, its all there you only see a small spectrum. In short, the human eye sees only in restricted levels required for our survival. Gamma, that's a hard fast wave that punches through matter and tears **** up. very quick high charges, hell overcharged atoms.
 

davenn

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Gamma, that's a hard fast wave that punches through matter and tears **** up. very quick high charges, hell overcharged atoms.

huh ?? ... that statement isn't very good and doesn't make much sense :frown:

Gamma rays don't travel any faster than visible light and very few of them penetrate the Earth's atmosphere

Have a read of this ......
https://imagine.gsfc.nasa.gov/ask_astro/ask_an_astronomer.html

from that link

Very few gamma-rays make it through the atmosphere. The atmosphere is as thick to gamma-rays as a twelve-foot thick plate of aluminium. Gamma-rays are very unlikely to go through that much material. However, they can strike the material and produce 'secondary' particles which are more penetrating, and can go through the material.

Most of the cosmic rays which reach the Earth's surface are 'secondary cosmic rays', produced by gamma-rays or (much more commonly) 'primary cosmic rays' hitting the top of Earth's atmosphere. These primary cosmic rays are high energy particles (such are protons and the nuclei from iron atoms) moving at very close to the speed of light. These primary cosmic rays have a hard time even getting to the top of our atmosphere--the Earth's magnetic field deflects most of them away. If Earth didn't have a magnetic field, there would be many more primary cosmic rays hitting the atmosphere, and many more secondary cosmic rays hitting us.
and this
https://imagine.gsfc.nasa.gov/science/toolbox/gamma_ray_astronomy1.html
 
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sophiecentaur

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The object detecting the waves etc.
That has nothing directly to do with the parts of the spectrum that make it to the surface - except in as far as evolution would not produce wasteful ability of 'seeing' frequencies that do not illuminate the ground so animals tend to have visual sensitivity mainly in the region of the spectrum between about 380 nm and 750nm (with some exceptions). Nocturnal animals will have little colour discrimination because high sensitivity is more important in very low light conditions.
 
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The object detecting the waves determine its viability, its all there you only see a small spectrum. In short, the human eye sees only in restricted levels required for our survival. Gamma, that's a hard fast wave that punches through matter and tears **** up. very quick high charges, hell overcharged atoms.
X-rays actually are seen - poorly, and of course without directional sensitivity.
Ability to sense ionizing radiation would be useful as well as feasible - but rarely needed, and absent for that reason. Many poisons lack taste and smell for the same reason.
 
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X-rays actually are seen - poorly, and of course without directional sensitivity.
Pls provide some reference on this one. I don't feel very comfortable with that. Are you talking about particular species?
 
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Pls provide some reference on this one. I don't feel very comfortable with that. Are you talking about particular species?
Yes. Man.
Quoting Wikipedia:
While generally considered invisible to the human eye, in special circumstances X-rays can be visible. Brandes, in an experiment a short time after Röntgen's landmark 1895 paper, reported after dark adaptation and placing his eye close to an X-ray tube, seeing a faint "blue-gray" glow which seemed to originate within the eye itself.[117] Upon hearing this, Röntgen reviewed his record books and found he too had seen the effect. When placing an X-ray tube on the opposite side of a wooden door Röntgen had noted the same blue glow, seeming to emanate from the eye itself, but thought his observations to be spurious because he only saw the effect when he used one type of tube. Later he realized that the tube which had created the effect was the only one powerful enough to make the glow plainly visible and the experiment was thereafter readily repeatable. The knowledge that X-rays are actually faintly visible to the dark-adapted naked eye has largely been forgotten today; this is probably due to the desire not to repeat what would now be seen as a recklessly dangerous and potentially harmful experiment with ionizing radiation. It is not known what exact mechanism in the eye produces the visibility: it could be due to conventional detection (excitation of rhodopsin molecules in the retina), direct excitation of retinal nerve cells, or secondary detection via, for instance, X-ray induction of phosphorescence in the eyeball with conventional retinal detection of the secondarily produced visible light.
Link 117 actually works:
Note that besides the experiment being potentially harmful, it's not done incidental to routine uses of x-rays. While head x-rays are undertaken for good reasons, direct seeing of them requires dark adaptation - and complete darkness would be unnecessary and hampering. The light is not bright, but too bright to see the x-rays.
 
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Interesting! Thanks for sharing.
Any volunteers for more experiments on this subject? :)
 

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