Re: Simple question on light from a non-physicist

survivalist@xxxxxxxxx a écrit :
I'm a layman and have an elementary question on physics.

Let's say I have a box constructed of opaque materials that is closed
except for one door in its side. I take a flashlight and shine it in
the box, and then close the door.

Opaque material... meaning non reflecting, I suppose.

What happens to the light inside the box? If I take the box into a
perfectly dark room and open it up, I don't think light comes out and
bounces around the room ;) Yet I think of photons/energy at a visible
wavelength coming out of the flashlight and going into the box.

If the inside of the box is made of opaque material, then most of the
light will be absorbed by the walls right off, raising the inside
temperature very slightly (your flash of light amounts to a very
tiny amount of energy), and whatever amount may be first reflected
will end up being completely absorbed on successive bouncing, each
of which will absorb most of the remaining light from the previous bounce.

At the speed of light, this will occur very quickly.

If your flash was short, very little energy will be communicated,
more if your flash was long.

If it's a function of how quickly the door closes, then what if the
door closes extremely quickly? Obviously, it can't close at the speed
of light.

Like I said, I'm a layman (and was a humanities grad at that!), so be
gentle.

If you are really interested in digging this a little, look for
texts on thermodynamics, black body, Planck's constant. Experiments
by Wien and Planck. Planck is the one who established the final
thermodynamics equation that allows calculating the exact particulars
of this type of interaction between light and matter.

André Michaud
.

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