Linked Questions
53 questions linked to/from How are classical optics phenomena explained in QED (Snell's law)?
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Snell's law starting from QED? [duplicate]
Can one "interpret" Snell's law in terms of QED and the photon picture? How would one justifiy this interpretation with some degree of mathematical rigour? At the end I would like to have a direct ...
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How can we explain, from quantum mechanics, why do we see light rays bend when light goes from one medium to another? [duplicate]
Refraction: I want a qualitative Quantum Mechanical explanation of why do we see light rays -in the classical picture- bend when light goes from one medium to another. I read that it is due to ...
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Why exactly does light bend when it enters a different medium? [duplicate]
Simply: what happens to the electric(and magnetic) fields when it enters the medium? How does it interact with the molecules and how this interaction leads to the bending of light?
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How does Fermat's principle of least time come from this statement? [duplicate]
In Wikipedia Fermat's Principle is stated as:
A ray of light prefers the path such that there are other paths, arbitrarily nearby on either side, along which the ray would take almost exactly the ...
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Quantum Electrodynamics explanation for refraction [duplicate]
I am trying to understand the fundamentals of Quantum Electrodynamics through the simple example of refraction. Let's start with a plane wave coherent state (or a number state) impinging on a boundary ...
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How does one derive Fermat's principle of Least Time? [duplicate]
Fermat's principle states that the path taken by a ray between two given points is the path that can be traveled in the least time.
I understand that Fermat's principle of Least time is crucial in ...
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What quantum mechanical property allows for reflection? [duplicate]
What are the quantum circumstances that manifest reflection?
Also, to what precision does the wave reflect and is that verified or only speculated by model?
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Derivation of Fermat's Principle from the Least Action Principle [duplicate]
Can I prove that Fermat's Principle (i.e. that light beam travels between two points in the path that require minimum time) using the Least Action Principle for electromagnetic wave? (from analytical ...
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QFT view of lower light speed of light in medium [duplicate]
In classical EM theory, if we have a medium whose dielectric coefficient is independent of wavelengths (suppose we filter the incoming signal to a certain frequency band), then the waveform gets to ...
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Do photons gain mass when they travel through glass?
Please correct me if I'm wrong, but I believe that photons slow down when travelling through glass. Does this mean they gain mass? Otherwise, what happens to extra kinetic energy?
I understand now ...
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Hamiltonian for relativistic free particle is zero
One possible Lagrangian for a point particle moving in (possibly curved) spacetime is
$$L = -m \sqrt{-g_{\mu\nu} \dot{x}^\mu \dot{x}^\nu},$$
where a dot is a derivative with respect to a parameter $\...
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Is Fermat's principle only an approximation?
Fermat's principle says that the path taken between two points by a ray of light is the path that can be traversed in the least time.
It occurred to me today that maybe the path is actually the one ...
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Why does light change direction when it travels through glass?
This was explained to me many years ago, by a physics teacher, with the following analogy:
"If someone on the beach wants to reach someone else that is in the water, they will try to travel as much ...
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How does light know which path is fastest?
We know from Fermat's principle of least time that light follows the fastest path. But how does light know which path is the fastest?
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Optics: Derivation of $\vec\nabla{n} = \frac{d(n\hat{u})}{ds}$
I have been given this formula from optics here, with no background:
$$\vec\nabla{n} = \frac{d(n\hat{u})}{ds}$$
Where $n$ is the refractive index and $\hat{u}$ is a unit vector tangent to the path $...
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