How do greenhouse gases affect visible and infrared light?

1 Answer
Feb 12, 2016

They do not effect visible light but they absorb infrared light.


Visible light wavelengths are smaller than 1 micron (0.4-0.8 microns roughly). Infrared technically from 1 micron to 1000 microns but is most intense at around 10 microns (infrared satellite photos are at 11 microns). The following chart shows which wavelengths #CO_2# absorbs.

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You can see that there are a few absorptive bands but none of them are in the visible light spectrum, they are in the near infrared and far infrared spectrum.

For methane the absorptive bands a a bit different but they are also in the infrared spectrum (more on the near side).

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You can see that both gases do not absorb at wavelengths in the visible light spectrum.

Water is a little bit more confusing because liquid water absorbs different bands than water vapor. Also, water vapor does absorb a small amount of visible light. Trying to find a good picture for water vapor and the other gases is difficult so I found one of all the gases. I hope it isn't confusing.

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