A General Question about Light

[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?

 

[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! :-)

 

[Graeme Robinson]

Great question! Yes, this is the right forum to ask about light.

To answer your first question, when you turn off the light switch, you are essentially breaking the circuit and cutting off the flow of electricity to the light bulb. This means that the light bulb is no longer producing light energy, and therefore the room goes dark.

As for your second question, if you had a light source in the middle of a room with only mirrors, the light would continue to reflect back and forth between the mirrors for a while, but it would eventually dissipate and the room would become dark. This is because mirrors are not perfectly reflective, and a small amount of light is absorbed each time it bounces off the mirror. Additionally, the air in the room would also absorb some of the light energy. So while the light would bounce around for a while, it would eventually be absorbed and the room would go dark.

I hope this answers your questions about light. If you have any further inquiries, please don't hesitate to ask.