Light Matter interaction

[gemma786]

Hi
I would like to ask that what makes a transparent medium transparent ? What happens when a photons of light passes through our atmosphere ?
I suppose that visible spectrum of light passes through atmosphere without causing excitation of electrons of gases' molecules, but what happens when photon doesn't excite electron and still encounter matter does it just passes through it or bounce back ?
In other words what is refraction? Is it passages of photons through interstitial spaces or absorption and then re-emission of same photons?

 

[srivi]

The molecular structure of liquids and the absence of structural defects are responsible for high optical transparency.
As light moves theough the atmosphere it continues to go straight until it bumps into a bit of dust or a gas molecule. then what happens to light depends on its wavelength and the size of the thing it hits.
when it hits large particles it gets reflected or bounced off. when it hits smaller than the wavelngth of visible light it may get absorbed and then radiated.

And go through this page which might help u

>> https://www.physicsforums.com/showthread.php?t=243807