Is it possible to trap light forever via mirrors?

 

 

see example:

 

So if I was to turn off the laser gun would the laser beam inside remain?

No. For one thing, mirrors would absorb about 5% of the light (if you used silver mirrors). Even if the mirrors were perfectly reflective, some light would eventually be reflected back out or into the laser.

If you can keep the mirrors cool enough, you could theoretically keep the light trapped for some while. But not forever.

Some lights take a while to go out totally after you turn them off. I would have thought there where better ways to (capacitise?) light.

Some lights take a while to go out totally after you turn them off. I would have thought there where better ways to (capacitise?) light.

 

Incandescent lights especially will give light for a brief but noticeable period after turning them off. In addition, your eyes continue to "see" an image for up to a few seconds after lights go out. The photons are dispersed faster than you can measure without very precise scientific instruments, even if the walls are covered with mirrors. If this were not true, why not just walk in a room of mirrors flip the light switch on and off quickly, and have that light for as long as you are there?

The time taken for thelight to decay can be used to measure absorbtion of radiation.

http://en.wikipedia.org/wiki/Cavity_ring_down_spectroscopy