What happens to all the light energy when you turn off a light switch?

Question

How is it that an entire room can be illuminated by one small light source, yet when that source is stopped, every trace of light is gone?

Is it just instantly absorbed by the surrounding surfaces?

I would think there might be a brief moment where the residual light is reflected back and forth between the walls or something.

Would the effect be the same in a room with a completely reflective floor, ceiling, and walls? Or would the light energy bounce continuously off the walls, keeping the room illuminated even in the absence of continuous source of light?

I'm sure there is a simple explanation, but please, enlighten me.

Answer 1

Imagine you have a filament (light source) exactly at the center of 100 % reflective ball shaped wall vacuum room.
When you turn on the filament, what will happened ?
All the light emitted by the filament are bounced back exactly to the filament. The filament will glow brighter and brighter until you turn off the filament or the filament melt, and the filament will still glow even though no electricity supplied to it anymore.
(The filament glows brighter and brighter because it receive the reflected ray of light and converted back to heat at the filament while energy is still being fed to it until you turn off.)
Why?, because no energy is left the room and no energy is absorbed by the wall.
This won't happened in real world, because there is no such thing like 100 % reflective or 100% vacuum.

Answer 2

good question
now,see it like this ---
when ur light source is on, u r continuosly suppyin light energy to the walls some of which is continuosly being reflacted back at the speed of [8*(10 to the power 8) metres per second]
and some of it is being absorbed by the walls.
u see the walls bcoz of the small amount of light that gets into ur eye after reflection (at a very high speed) hence, u see objects instantly.
the small amt. of reflec. light energy that falls into ur eyes gets converted to chemical energy of the brain via the nerves.
whereas the rest is absorbed by the surroundings
its so fast that it seems as if no time has elapsed
s'pose if there was no continuos energy, then we would have fallen short of the light

and to ur 2nd question --- bout reflctive surface ... u have described what appens ina diamond, thats why it sparkles!(bcoz it traps light energy)

ok? so now i think u've understood the concept nicely?

Answer 3

When you turn of power to an incandescent light for example, light source of emission does not switch off instantaneously. The reason is that the fillament takes time to cool and light energy atenuates but there is still emission in the infrared region.
Your eye may not detetect it and you think there is no more light ,but there except its is for a short amount of time. The residual emission is at a different frequency and will be absorbed in the surroundings as heat energy into the atomic structure of the walls or other objects.
Note the glass in the mirror still absorbs infrared rays and experiences a minute change of temperature.

If you understand the nature of light as timy mass structures than you would say they are very ellusive entities,they seem to penetrate every where.

Answer 4

I simply treat the low energy bulbs in the way I did with the old type. Turn them on and off as required. I have used them for about 9 years now and never heard that they should be left on. In fact the initial bulbs came as a 'freebie' from the utility company EON with instructions for use, no mention being made as to leaving them on. My only gripe is that it can take a while before they reach full brightness. I turn on my outer porch light so that I can put rubbish in my wheelie bin, and find that I have usually completed the task before the bulb has achieved full brightness, so I now use a flashlight. The plus side of low energy bulbs is that they last a long time. As for the kettle I always have it about a third full.

Answer 5

It is absorbed, sorry to burst your bubble, even the average mirror is only 40-50% reflective.Just your eyeballs alone would absorb those few photons, that just so randomly have to randomly strike the back of your retina, doesn't mean there are not photons there, a special camera prob would detect a short burst before the 'wave' crashes and is absorbed, if you believe in the wave theory

Answer 6

considering the speed of light is 299 792 458 metres per second I dpubt you would have a chance to see an reflected light bouncing off each surface until it's fully absorbed... you would have more change of catching a bullet between your teeth

Answer 7

constantly, as long as there is light, there is color, right now, everything you see is asorbing light, at a constant rate, when you remove the light source, they stop absorbing it at the speed of light, faster then the blink of an eye. as for a mirror wall, the mirror reflects off something so since there really is no solid colored substance there is nothing solidly reflected

Answer 8

Well, for starters, there IS residual "light" when you turn off the bulb. The problem is that seeing as light travels at 186,000 miles per second this risidual light "goes away" too quickly for us mere humans to detect it.
The energy that was being converted into light from electricity is re-routed back into your enrgy grid. (it needs a completed circuit to be converted into light (which is really the offshoot of its being converted into heat.)

Answer 9

Remember it is going the speed of light. It does get absorbed,just takes a little longer in your reflective room. just a little longer instant Hopes this helps.

Answer 10

The radiation from the source(light bulb)is emitted omnidirectionaley. When you turn off the source, that radiation is no longer reflected from the surfaces in its vicinity.