All Questions
154
questions
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How to use dipoles to enforce the boundary conditions for a spherical dielectric with complex permittivity
I want to impose an electric and magnetic field on a spherical dielectric of radius $ R $ and relative permittivity $\epsilon_r=\epsilon'+i\epsilon''$. Say the fields are slowly-varying (like a plane ...
- 1
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2
answers
123
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Diffraction when the wavefront is not parallel to the plane
I am studying Feynman's chapter on the origin of the index of the refractive index (see this link).
If I am not mistaken, what he does is to prove that when a wave enters a medium (modelled as a ...
- 507
1
vote
1
answer
52
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Confusion regarding phase
As far as I know about phase if the phase difference between two waves is positive, the former is leading..and the latter is lagging. Then why has D J Grifith stated this?
If the phase of the magnetic ...
7
votes
5
answers
14k
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Light waves can't have a wavelength
The wave nature of light comes from Maxwell's equations. More precisely, the two wave equations that come from them:
$$\Delta\vec{E}=\mu\varepsilon \frac{\partial^2\vec{E}}{\partial t^2}\\
\Delta\vec{...
- 267
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1
answer
47
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Why are Fresnel coefficients not symmetric?
When talking about reflection, we have the following coefficients for the electric field:
$$r_{\perp}=\frac{n_1\cos(i)-n_2\cos(t)}{n_1\cos(i)+n_2\cos(t)} \\ r_{\parallel}=\frac{n_2\cos(i)-n_1\cos(t)}{...
- 267
1
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1
answer
51
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Why isn't the original EM wave in a beam of light in a medium not still detectable from a distance as if it were moving at the speed of light?
I'm learning optics and I've been told that the reason light slows down in glass is because the Electromagnetic field of a beam of light interacts with and accelerates charged electrons in glass ...
- 531
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1
answer
31
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Effect of incident angle on wavelength of transmitted wave for normal polarisation?
In my electrodynamcis assignment I'm being asked to derive the wavelength of a normally polarised wave transmitted through a glass/air interface as a function of $n_1$ (the refractive index of the ...
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30
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Polarization of electric field and its effect on the Poynting vector
To preface, I've little experience with optics. This is a very use-case specific project I'm undertaking. So, if there are any improvements in my method, I'd appreciate it!
I'm working with the vector ...
1
vote
1
answer
50
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Huygens Light Theory using Spheres and Miller's recent discovery?
Huygens writes in "Treatise on Light" a theory that propagation of light through the aether can be explained using Spherical waves emanating from every point and they interfere. Miller ...
- 245
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1
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92
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Energy of Monochromatic Beam of Light
A monochromatic beam of light has energy
$$ E_{\text{beam}} = N \hbar \omega, $$
$ N $ being the number of photons in the beam and $ \omega $ their frequency.
Another way to evaluate this energy is ...
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1
answer
46
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Help with dispersion relations for EM waves in anisotropic dielectric materials
I am really struggling to understand the following dispersion relations which we derived in class.
For an electric field in the z-direction, we have:
$$k^2_x + k^2_y = \frac{\omega^2}{c^2}n_z^2\tag{1}$...
- 155
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2
answers
66
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How to use the boundary conditions of electromagnetic waves to derive the refraction law of light?
In my book it says we can use the boundary conditions of electromagnetic waves to derive the refraction law of light. How to derive it?
- 353
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0
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23
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Are Transmission values for absorptive light filters proportional to Intensity?
Mostly filter rates are given in percent, but if I imagine that for example 10 photons hit an absorption filter with 50%, molecules are excited there and in the end only 5 get through while the other ...
- 211
2
votes
1
answer
59
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Can the time varying Intensity of an electric field of a wave be measured?
Lets say that we have a detector which we use to measure the intensity. Theoretically, the intensity is a varying function of time (When we calculate the Poynting vector) but often in textbooks they ...
- 21
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46
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What happens in a conductor when the electric field has a plasma frequency?
The complex index of refraction for a conductor is given by the equation: $$N(\omega)=n+ik=\sqrt{1- \frac{\omega_p^2}{\omega^2+i\gamma\omega}} $$ where $\omega_p^2=Nq_e/\epsilon_0m_e$ is the plasma ...
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