If you had a box made out of Mirrors?

Question

If you had a box made out of Mirrors and if you where able to get a very small light source to project into the box. Would it completely light up or just kinda stay the same brightness. Hope this makes sense?

Answer 1

When we see or measure light, it is an instantaneous measurement.

As the light keeps shining into and reflecting inside of the box the light keeps "accumulating."

Answer 2

There would be a lot of light in the box. The mirrors absorb a little, so you wouldn't have infinite light, but it would get quite bright in there.