Light disappearing

[Diablod666]

if you were to turn on a light, and place two mirrors facing the light either side of it, so that light would hit the left mirror then bounce onto the right, then back to the left etc. then why, when you turn the light off, does the light disappear? surely it should continue bouncing between the mirrors until something stops it?

[Tweed]

It looses energy at impact. The energy is converted into a different form

[NetSquirrel]

Yes - you cannot build "perfect" mirrors. Even if you did have perfect mirrors, a typical light source would shine light in all directions, so that virtually all of the emitted light would not be at the necessary 90� to the mirrors in order to be reflected back and forth indefinitely.

[Ralph]

You also need to remember that you cannot directly see light, you just see the effects of light. If you could see light, you would see nothing else! Maybe a very small amount of light in your proposed experiment does bounce back and forth indefinately, but when you try to measure this, you've ruined the experiment. Heisenberg's Uncertantity Principle on a small scale? Probably not.

[Diablod666]

thanks for that, great answers, helped a lot =D

[anthomson]

eh! not sure what happened there - think my answer got trapped between two mirrors. 

I was going to add that the photons in a laser are effectively trapped between two mirrors. When enough photons have been trapped they are allowed to escape as a concentrated beam of light.

[Dagman]

Ah, but, what if it does bounce between them, the only problem is observing it which means interfering with its path which in turn may stop the cycle. So you could never know!