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Fate of Photons
Name: Ryan E.
Status: student
Age: N/A
Location: N/A
Country: N/A
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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Update: June 2012
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