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linux kid
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I did a search for optical accelerator but it's not clear to me exactly what is being discussed. If so, has the been an invention to do this?
pete5383 said:What if a photon is traveling from one medium to another, both with different indices of refractions (like from air to water)? The velocity of the photon would change upon entering the second medium, would that not be considered an acceleration? Or am I missing something..
pete5383 said:What if a photon is traveling from one medium to another, both with different indices of refractions (like from air to water)? The velocity of the photon would change upon entering the second medium, would that not be considered an acceleration? Or am I missing something..
ranger said:Umm...were a couple of responses deleted here? I'm confused...
Is this true? I thought photons are absorbed and new photons re-emitted, from a mirror.Claude Bile said:While the speed of light is constant, the velocity of a given photon most certainly isn't. Mirrors for example technically act as photon accelerators by changing the direction of propagation of photons.
While the speed of light is constant, the velocity of a given photon most certainly isn't.
lightarrow said:Is this true? I thought photons are absorbed and new photons re-emitted, from a mirror.
lightarrow said:Is this true? I thought photons are absorbed and new photons re-emitted, from a mirror.
Ok. But I haven't completely understood what happens.vanesch said:I think that some confusion about "the speed of photons" comes about because we forget how photons are defined, and start thinking of it as little "light bullets", or "wave packets" of classical EM radiation.
In free space, photons are defined as the different eigenstates of the energy and momentum operators of the EM field. It turns out that they correspond to harmonic oscillator solutions for each and every mode of the classical EM field, which, in free space, comes down to plane harmonic waves. So to every classical plane harmonic wave corresponds a quantum-mechanical harmonic oscillator (you know, with energy levels E_n = (n + 1/2) hbar omega), and we call the steps between these energy levels: photons.
If there is a dielectric, we can treat the situation in two different ways. We can have a kind of semiclassical approach, where we look first at the *classical* modes of this setup, and then assign again quantum mechanical oscillators to each of these classical modes, and call them "photons". Or we can treat this dielectric as a quantum-mechanical system which *couples* to the free EM field.
In the first case, you understand that the "photons" of this semiclassical system are ENTIRELY DIFFERENT states than the photons of the free EM field. They are eigenstates of a totally different problem, and hence the "free EM photons" have not much to do with the "semiclassical dielectric photons".
However, because the dielectric interaction has been taken into account (classically), there is no "interaction of these photons with the dielectric": it is already included in the classical field solutions that were to be quantized.
In the second case, the interaction terms between the free EM field and the quantum mechanical dielectric system, which induces transitions between the "free photon states", because of the couplings (perturbations) introduced by the dielectric (seen as a quantum system that introduces interaction terms in the EM hamiltonian).
lightarrow said:Ok. But I haven't completely understood what happens.
Let's say a single photon is involved in the process. How could you explain it in simple terms (if it's possible)?
lightarrow said:Is this true? I thought photons are absorbed and new photons re-emitted, from a mirror.
Claude Bile said:Reflection is not an absorption/emission process, nor is transmission through a transparent medium.
Darryl said:Light in a vacuum is the one or stream of photons of light, they travel until they strike some mass, they are absorbed into that mass. If that mass is made of certain stuff, when the light is absorbed, at almost the same time another photon of light is emitted.
How does the new photon "know" in which direction to go in order to be properly reflected (or, sent) in an optical instument?
OF
Yes, photons can be accelerated. According to Einstein's theory of relativity, the speed of light is the highest attainable speed in the universe. Therefore, photons can be accelerated up to the speed of light, but no faster.
Yes, photons always travel at the speed of light in a vacuum. This is a fundamental constant of the universe and cannot be exceeded.
No, according to Einstein's theory of relativity, the speed of light is the ultimate speed limit in the universe. Nothing can travel faster than this speed, including photons.
The speed of light is directly related to the acceleration of photons. As photons are accelerated, their speed increases until they reach the speed of light. However, they cannot be accelerated beyond this speed.
Yes, photons can be slowed down or even stopped when they pass through a medium such as air or water. This is because the photons interact with the particles in the medium, causing them to lose some of their energy and therefore slowing down. However, this does not change the fact that photons always travel at the speed of light in a vacuum.