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Name: Ryan E.
Status: student
Age: N/A
Location: N/A
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Date: N/A


Question:
Light is made out of photons. Then when you turn off the lights in the room where do they go? Do they get absorb by some kind of subatomic particle?



Replies:
The photons travel in a straight line from the source. Eventually, the photon is absorbed by molecules in the surroundings, or reflected or scattered depending upon the setup. If absorbed the photon may be converted into several photons of lower frequency (i.e. energy).

Vince Calder


Ryan,

The photons go the same place they go when the light is turned on. The photons are traveling through the air at three hundred million meters per second. They can travel the length of three million football fields in one second. They are emitted by the light source. Some are absorbed as soon at they make contact with a surface. Some reflect from the surface. Some of the reflected photons enter your eyes. This is how you see the object that reflected the photons. Some of the absorbed photons come back out as lower energy photons (infrared light, radio waves). Some of the absorbed photons warm the surfaces. Eventually, all photons in a room will be absorbed or will pass through a window or a doorway.

Dr. Ken Mellendorf
Physics Instructor
Illinois Central College


Ah! Light! - we see it everywhere - but still have no real idea what it is.

Some scientist have observed that light behaves as particles (photons) and it has also been observed to behave as a wave. The general consensus seems to be that it is a little of both and not quite like either.

When you turn on the light in your room, photons stream from the filament and bombard everything in the room. Some are absorbed, and cause a slight increase in temperature. Some bounce off. Depending on the energy of the ones that bounce off, different objects have different colours. Some photons even enter your eye, where they cause microscopic excitation of light sensitive molecules in the back of your eye, and it is the actions of those molecules which allow us to see.

When you turn the light off, any photons bouncing around the room are quickly absorbed by the surfaces of the room. Since light travels at about 300,000,000 metres per second, it can bounce around your room a million times before being absorbed, and you would still say that the darkness was instant.

Since photons have no mass (at least when they are standing still) and their momentum is infinitesimally small, their total effect in your room is impossible to measure in normal circumstances.

Nigel Skelton



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