Question

what causes the photons to be released from friction

Answer 1

Photons are released because there was energy put into the system. So when two atoms rub against each other, an electron may jump to a higher energy level from this inputted work. After a fraction of a second, it "relaxes" and the electron drops down to its original energy level, and because of conservation of energy, it releases a photon of light.

Answer 2

This concept is used in the principle of laser action.

Answer 3

Dofborg, does the e- always relax to it's original energy level?

Answer 4

Depending on your material, it may not. If it does not, there is a potential created in the material simple called "holes".
http://en.wikipedia.org/wiki/Laser_diode

Answer 5

thanks dofborg