Can light be trapped?

Hmmm. While talking to some friends this came up, can a beam of light be trapped? Kind of like inside a sphere where the inner surface is polished to a mirror, would light bounce inside it forever or would it fade away?

Another one, What part of the atom sheds the photon when exited?

Thanks!
AlexGT

The photons get kicked out when an electron returns from an excited state to it's resting state and sheds the excess energy.


Scientists have come up with a material that can slow down light dramatically (in the mph range) but I havent heard of light actually being trapped.

So the electron sheds the photon? And would an element that is shedding photons transmutate to a different element?

What you describe would theoretically work if the reflection was 100%, and there is no such thing in reality.

However, I recently saw a science program on TV where a scientist had devised a way to slow light so much that she was able to make it come to a complete stop in a supercooled fluid cloud until released by a triggering laser pulse. The show didn't have much real detail on how the process worked exactly.

What is happening on the atomic level when a photon is released is that an electron is moving from one orbital path around the nucleus to a lower energy orbit that is closer to the nucleus. This excess energy is released as a photon of light.

So in theory an atom can emmit light and change elements because its loosing mass (The photon) until it becomes a hydrogen atom then it looses the last electron in the form of light, and dissapears? Correct?

AlexGT

http://www.google.com.au/search?hl=en&q=light+inside+a+mirrored+sphere&btnG=Google+Search&meta=
Norm

Yes, the electron releases the excess energy packet as a photon.

AlexGT said:

So the electron sheds the photon? And would an element that is shedding photons transmutate to a different element?

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Photons are a release of energy. When an atom gain or sheds an electron, it stays the same element but it becomes an ion with a charge. The element is determined by the number of protons. As long as that doesn't change, it remains the same element. If a neutron is gained or released, it becomes an isotope of the same element.

The electrical charge is dependent on the number of electrons, not their energy.

Imagine a person driving around the world in a car. That's like being in the ground state (the lowest available energy level). Now imagine a person flying around the world in a spaceship. They're higher up, and going much faster, and have a lot more energy. But either way, there's still only one person travelling around the earth.

The photon is massless, it is only energy. It's not a part of the element. If you have elements in an excited state (electrons are orbiting high and fast), they will drop down. The excess energy becomes a photon. If you're in the ground state (low and slow), and get hit by a photon, you'll absorb it and bounce up to the excited state.

The electrical charge doesn't change, nor does the mass. Just the energy.

AlexGT said:

So in theory an atom can emmit light and change elements because its loosing mass (The photon) until it becomes a hydrogen atom then it looses the last electron in the form of light, and dissapears? Correct?

AlexGT

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I think you're confusing photon's with protons

AlexGT said:

Hmmm. While talking to some friends this came up, can a beam of light be trapped? Kind of like inside a sphere where the inner surface is polished to a mirror, would light bounce inside it forever or would it fade away?

Another one, What part of the atom sheds the photon when exited?

Thanks!
AlexGT

Click to expand...

It's a thought exercise, because there is no such thing as a 100% reflective surface.

Some energy will always be lost to heat, as the photons collide with atoms that comprise the reflector. Therefore, any light "trapped" inside would rapidly disappear.

Therefore, as far as I know, there is no current physical framework that would allow the kind of an object that you're describing. Certainly, it would be incredibly useful if it could be developed, due to the ability to store an infinite amount of energy inside. However, our current understanding of the laws of physics does not allow for such an object to exist.

The only thing that's similar to what you're describing would be an object with sufficient mass concentrated in a small volume, wherefore the curvature of space-time would be completely orthogonal, and thus light would no longer be able to get out. In other words... a black hole.

DonShock said:

However, I recently saw a science program on TV where a scientist had devised a way to slow light so much that she was able to make it come to a complete stop in a supercooled fluid cloud until released by a triggering laser pulse. The show didn't have much real detail on how the process worked exactly.

Click to expand...

I saw that show too, It was an episode of The History Channel's The Universe, "Lightspeed". The work was done by Dr Lene Hau at Harvard University. The explanation was very vague. They compared it to teleportation. They are OUT THERE

Nova episode on PBS:

"Absolute Zero: The Race for Absolute Zero"

Very cold temp, very close to Aboslute Zero (Zero Kelvin) can be used to slow down light to a standstill, effectively trapping it.

Actually photons have mass they can be trapped by sufficient gravitational feilds, I cant explain it as well as somebody out of highschool minght be able to but if there is anyone on the forums with a decent understanding of quantum mechanics they would be able to tell you that a photon acts not only as a "massles" particle of energy (or wave) but it can also be a electron which does have mass... like I said its getting into quantum mechanics which I dont quite have a full (or partial ) understanding of....

tay said:

The photon is massless

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not bad coming from a sophmore right?
Daniel Coble


EDIT: the bose einstine condensate is capable of slowing light down to about the speed of a bicycle

Youfoundnemo said:

EDIT: the bose einstine condensate is capable of slowing light down to about the speed of a bicycle

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That's what I was thinking of. I was watching that show out of the corner of my eye one day and I remember the part about being able to slow down light to the mph range. Thanks for the memory jog on the name of that custom soup they used.

Youfoundnemo said:

Actually photons have mass they can be trapped by sufficient gravitational feilds, I cant explain it as well as somebody out of highschool minght be able to but if there is anyone on the forums with a decent understanding of quantum mechanics they would be able to tell you that a photon acts not only as a "massles" particle of energy (or wave) but it can also be a electron which does have mass... like I said its getting into quantum mechanics which I dont quite have a full (or partial ) understanding of....



not bad coming from a sophmore right?
Daniel Coble


EDIT: the bose einstine condensate is capable of slowing light down to about the speed of a bicycle

Click to expand...

Frankly, I don't really 'get' the more complicated quantum mechanics, besides the basic Bohr/Heisenberg/Schroedinger tenets like - wave/particle duality, quantized energy levels, distinct quantum numbers (n, l, m, s) with one and only one electron for each number, photoelectric effect: the 'simple' Modern Physics where the photon is in fact a massless particle. We've still got just 3 spatial and 1 temporal dimension, and our subatomic particles are still limited to proton, neutron, electron, positron, and photon. When this simplicity is gone, I am sure I will miss it, and file it with geometrical optics, frictionless surfaces, the small angle theorem, and other fun but ill-fated assumptions.

My point is simply to dispel the assumption of a previous poster that a photon was a mass particle contained within an atom, and gained or lost during ionization like an electron. We treat the photons as quanta of energy, and an high energy electron can become a photon and a low energy electron, or a photon and a low energy electron can become a high energy electron, photons can be gained or lost without changing the mass of the element - they are not conserved during events like an electron is (they can be spontaneously created or destroyed). Only the energy that they contain is conserved.

Bose-Einstein condensation? That's when the windows get fogged up in the winter, right? :sick2: I usually just use my car's defroster.

Ouch, I think Ive been schooled, you just listed off atleast 10 things that flew over my head:candle: (hopefully 12th grade sci will help me figure out some of what you said) I didnt realize that you were trying to help a fellow CPFer out whith the assumption that a photon was part of an atom

I'm not sure where people keep getting the incorrect idea that photons have mass. (This claim comes up again and again.)

Massive particles must always travel at speeds slower than c (the speed of light in a vacuum). Light is made of photons, so if photons had mass, then the conclusion would inevitably be that light cannot travel at the speed of light.

If a photon doesn't have mass, how is it that it can be affected by gravity?

AlexGT

I thought that a photon wasn't truly a particle but simply could behave as one.