Subject: What is the light loss rate in a box (mirror, etc) of ultraviolet light?

Question is that if you created a light beam that matched the frequency of the 
mirror that was placed in front of it in a vacuum, and placed an identical 
mirror at the other end and aligned them so that they will reflect back and 
forth. Will there be any energy loss (at what rate is it lost (I read this in 
an article response)? If so, how much (I will then calculate the loss in 
energy (Percent or energy level, to see how long it will last)? The light 
bounces back and forth in a vacuum just between the mirrors. My next question 
is that I have looked into the interaction of material and photons in respect 
to their frequency and matter. However, I have found contradicting data on the 
interaction of photons on each other. If two electrons bounce off each other, 
what happens? I have read that two beams of light hitting each other will at 
their incident angle disperse. However, will the photons lose energy? My next 
question is that what the best reflecter of light/Ultraviolet light is. I have 
read that snow is the best reflector of light. However, I am told to find out 
the next best light in respect to the spectrum of light that is (visible and 
ultraviolet) listed above. What is the best for this (Mirror, metal, glass, 
etc)? How to you tell.

Re: What is the light loss rate in a box (mirror, etc) of ultraviolet light?