If I turn on a light in a room made of mirrors, will the light ever fade once the bulb is turned off?

Answer 1

This is one of the age old wacky questions, like "if a tree falls in the the woods but no one is around to hear it, does it make a sound?" It also kind of spins off of one of my favorite impossible topics "perpetual motion". Basically, If (and that is a big "if") you could build a perfect room in which to contain the light then yes you could contain the light, for a time.

However, no such room can exist. The first problem I see is mirrors that composed the interior walls, would have to be "perfect" mirrors. That is, would have to reflect all the light as light energy, when in reality each time the light contacted the mirror to be redirected to another part of the room, some of the lights energy would be lost as heat energy conducted out through the walls of the room. eventually leaving you with an unlit room. considering the speed at which light travels this "eventuality" would come rather quickly.

Second is the fact that you would not be able to be in the room or would you be able to use the light for anything. So, back to the tree falling... if you COULD store the light indefanatly, what would be the point?

Answer 2

Cute

If all mirrors were perfect i.e. reflected light w/o any loss of energy, and if the room was a perfect void (not just no air, but no particles with which photons might interact), then no, the light would never fade.

But in practice, such a "perfect" room cannot be built. So the reflections would all disappear as soon as you'd turn the bulb off.

hope this helps

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Answer 3

Light only travels at a constant speed in a vacuum (299,792,458 m/s) and thus, looses energy when moving in, between, and reflecting from, different mediums. The nearest we can get to perpetually propagating light is by exploiting total internal reflection, e.g., as in fibre optics, but this still requires a constant light source.

It is likely that as you turn the bulb off the last light waves will be emmitted from the source and then become infinitely diffuse (and loose energy) with every reflection (note also the light travels in a straight direction). This will occur very rapidly - i.e., much faster than you will be aware - but, theoretically you woud notice the room becoming progressively dimmer if you could slow light speed down ...

Answer 4

I lurve these question about the nature of light! I could lap them up with a spoon! I would love for someone to tell me about it. It is not a particle, it is not a wave, it is not either, it is not neighter and it is not both. When don't look at it, it is what you want it to be like, when you do, it behaves as if we only see the behavioural tip of its quantum iceberg and is the greatest postural dichtomy we know. Coupled with this is the different sexual maturation rates we have as a species and the fact that men believe everything women say and that women are deliciously curious and suspicious about men. It is an interesting world isn't it? If God was taking the piss when he made us I wouldn't be surprised. But from what I hear, he has gone off elsewhere to work on a more ambitious project and has forgotten us. Selah.

Answer 5

Mirrors are not 100% efficient so some of the light is converted to heat in the mirror. So the light will gradually fade depending upon the actual efficiency of the mirrors at reflecting light.
Also, if you are in the room, you will not reflect all the light that falls on you.
Any detector that you use to detect the presence of light will also not reflect all the light.

Answer 6

Yes, because the mirrors do not reflect 100% of the light, aluminum mirrors are only about 70% effective, and silver about 98%. The speed of light is so fast, so best case it will all be absorbed after about only 50 reflections. The speed of light is so fast it will seem instantaneous.

Answer 7

yes it will go away instantly, as the speed of light is almost instantaneous, once the source is gone then light will stop reflecting, it like electricity, in a wire, if U could join up a wire instantaneously after putting power though it, the power would not keep on going around the wire, its the same with the light

Answer 8

Of course. Once the source has been turned off, there will be no light to reflected. If it didn't fade, you'd be in a spot of trouble with the laws of thermodynamics.

Answer 9

Definitely yes. The light fades, but actually it is transformed to another sort of energy, most probabely it will increase the temperature, by increasing the molecular motion in the space of your experiment. If you have a strong enough thermometer, you might even measure it!

Answer 10

the light shall fade out coz the mirrors cannot reflect 100% of the light. they do absorb some %age of it.