I thought that when things bounced off other things they imparted more momentum (twice) then if they are just absorbed. since heating things is like imparting momentum to the molecules that make up the substance, and light does exert pressure, why is it that things that absorb light tend to heat up more than things that reflect it?
2007-10-24 22:24:29 · 5 answers · asked by keyahnoo 2 in Science & Mathematics ➔ Physics
Good thinking! You are correct, the photon does impart momentum when absorbed (inelastic collision) or reflected (elastic collision). Imparting momentum need not result in heat. But the energy of the photon is cp, or the momentum multiplied by the speed of light. The black object absorbs the photon and its energy, converting the energy of the photon into kinetic energy of the particles in the object (heat).
Note that the momentum property is useful in the solar sail.
2007-10-25 12:19:16 · answer #1 · answered by Frank N 7 · 1⤊ 0⤋
heat energy goes with the light energy in the laser.
black objects just absorbs much of the light, thus absorbing much of the heat.
mirror reflects the light thus bouncing off the heat.
there is no momentum in light since light is not an object but energy. when there is momentum there should be mass. only objects have mass. one evidence light doesn't have momentum is that it has a constant velocity, light doesn't accelerate or decelerate.
the black objects are being charged with heat since they absorb more light than bouncing it off and light goes with heat.
mirrors are less charged with heat since it reflects more of the light than absorbing light.
2007-10-25 05:43:29 · answer #2 · answered by jerriel 4 · 0⤊ 2⤋
Black objects absorb most of the light tht hits them, that's why we only see black because most of the light is absorbed. Light is a form of energy. Energy cannot be created or destroyed. So the objects get hotter.
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2007-10-25 05:36:03 · answer #3 · answered by Zorro 2 · 1⤊ 0⤋
a mirror reflects more heat than black sucks in
2007-10-25 05:45:05 · answer #4 · answered by virgil 6 · 0⤊ 0⤋
in reflecting there is no need to get involved with the ray..... and it's easier to reflect....... but in absorbing
firstly the substance tries to absorb the rays and then tries to reflect radiate them back....... but the radiated energy is much less ........ much of energy is lost in absorption.......
main point: reflection is a surface phenomenon but absorption is not.......
2007-10-25 05:38:17 · answer #5 · answered by dr. know all 2 · 0⤊ 1⤋