"When a package of light energy (or photon) hits a solid object, three things can happen:
1)
light can disappear - if the photon has the same vibrational frequency
as the electrons and the material it strikes, those electrons absorb its
energy, changing the photon from light into heat.
2) light can also
be scattered - the surface electrons can grab the photon's energy and
then eject a photon of the same wavelength, which is how you see pretty
much everything that doesn't emit light on its own.
3) transparency
- if the photon doesn't have the right vibrational energy for
absorption and if the atoms and the material are arranged and patterns
that discourage reflection (such as the random jumble of molecules in
glass or air), then the photon's energy passes from atom to atom, some
emerging on the other side still bright and shiny. Then
you have transparency."
from Discover magazine
July 2012
by Jason Daley
