Theoretically would light infinitely bounce, in a room made of perfect mirrors?

Asked by: N.N.

Answer

Yes, light would bounce forever in a room made of perfect mirrors. A perfect mirror reflects all of the light incident on it according to the laws of classical optics. There is no loss through either transmission of the light or conversion of light energy into another form (atomic vibrations, etc.). However, this scenario breaks down when real mirrors are used. Since mirrors are made of atoms, and not perfectly-flat perfectly-reflecting surfaces, all of the light is not reflected. Thus, light will not bounce forever if we use real mirrors, the light intensity would decrease with each bounce.
Answered by: Andreas Birkedal-Hansen, M.A., Physics Grad Student, UC Berkeley