Greenhouse effect (reflection vs transmission)

  • Thread starter klng
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Hi,

In the study of the greenhouse effect, I know for a fact that short wavelength radiation pass through a glass container and heat up its contents. When its contents get hot, they will re-emit longer wavelength (and hence lower energies) radiation, which will then be unable to pass through the glass anymore,but is reflected back into the glass container, where it will stay.

How does the wavelength determine whether light is reflected from or transmitted through a glass block?

Does the answer have anything to do with the quantum energies of an atom?

Thanks
 

vanesch

Staff Emeritus
Science Advisor
Gold Member
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Essentially, yes. It is the quantum mechanics of the electron clouds in the material which determines which photons are scattered and/or absorbed. Whether this is on the atomic, molecular, crystallographic or other level, depends on the radiation in question and the kind of material.

It comes down to knowing whether there is an interaction between photons of said energy (wavelength) and the electron cloud.
 
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klng
Thought you might find the following of interest although not directly related to your question. This is from a lecture by Roger Penrose commemorating Stephen Hawkings 60th birthday, Cambridge England, 2003, (The title does not sound like it relates to your post, yet he had an interesting paragraph that DOES!) "The problem of spacetime singularities:implications for quantum gravity"

.. we get energy in a low entropy form (from the sun) and this has to do with the fact that the sun is a bright spot in an otherwise dark sky. ..we can only take advantage of the temperature imbalance...and the visible light is in the form of relatively small numbers of photons, with small numbers of degrees of freedom, and the energy that feeds back into space is is infrared and each individual photon is much less energetic so there have to be many more photons to carry this same energy away:the energy is spread over many more degrees of freedom
 
22
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Thanks a lot for the replies! :!!)
 

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