# A General Question about Light

1. Dec 2, 2004

### Smurf

Hope this is the right Forum

Ok, so light is a form of energy created by a number of Phenomena, it is created and then it.. moves.. and it bounces off of stuff and keeps moving. So why is it when you turn off the light switch, that the room suddenly goes dark? What causes the light to shift forms?
What I really want to know though is what would happen if you had a light source in the middle of a room with nothing but mirrors on the inside, and then suddenly look away the light source, would the light keep reflecting back and forth for ever?

2. Dec 2, 2004

### Tide

Suppose that 99.99% of the light that strikes a wall (mirror) gets reflected (i.e. only 0.01% gets absorbed. If the average distance between bounces is, say, 30 feet then over the course of 10 ms (about the shortest interval of time you can perceive) the light will have reflected about 300,000 times. Evaluate $0.9999^{300,000}$ which will give the amount of light remaining and then try to answer your own question! :-)