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Questions tagged [electromagnetic-radiation]

Propagating solutions to Maxwell’s equations in classical electromagnetism and real photons in quantum electrodynamics. A superset of thermal-radiation.

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Can two semi-infinite plane waves undergo perfectly constructive interference?

This is building off of a question I asked here. When discussing the linked problem with some friends, the consensus seemed to be that the reason two identical semi-infinite plane waves cannot ...
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2answers
25 views

Electromagnetic radiation from sun and human body

What is the difference between infrared radiation produced in sun and thermal radiation, in infra red range, by human body in terms of its energy or are they the same?
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4answers
71 views

In $E=hf$, can $f$ assume any positive value? (Beginner) [duplicate]

The energy of photon is given by the equation $E=hf$, where $h=$ Planck's constant, and f=frequency of radiation. Is f quantized, or can it assume any value? If it can assume any value, then wouldn'...
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Electromagnetic waves in a perfect conductor

What happens when an electromagnetic wave strikes a perfect conductor at normal incidence? Is the wave transmitted or reflected through the conductor?
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Do transpired solar collectors use both visible light and infrared waves to produce heat?

Because black non-glazed transpired solar collectors absorb both visible light and infrared waves, are both waves equal in stimulating heat?
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3answers
90 views

What was shocking in Einstein's partcile theory of light?

I know that when Einstein proposed the particle theory of light it was revolutionary and shocking for most of physicists and it took years to accept that view. Particle theory had been proposed in the ...
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44 views

Propagation of Electromagnetic Waves

I have studied that EM waves propagate due to the perpendicular oscillations of electric and magnetic fields with respect to each other. I read the statement as It's propagation can be interpreted ...
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1answer
24 views

Energy conservation in the combination of two coherent beams

I was asked a question today by a student that I couldn't find a satisfactory answer to. Imagine we have two identical laser beams with average electric field strength $E$. Upon combining these beams ...
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1answer
34 views

EM spectrum and sense of sight

If we cant see all the spectrum does this mean that maybe exist objects we cant perceive? or it just the colors we cant perceive?
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2answers
59 views

Is there a link between nuclear radiation and sound? [closed]

I'd like to understand if it's possible to relate/imagine a link or relationship between nuclear radiation and sound. A simple description would be appreciated since I don't have a deep understanding ...
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What are these radial and azimuthal “$s$ and $p$ polarization” vectors for a free-space EM beam representation?

I'm reading the rather interesting recent paper Role of Radial Charges on the Angular Momentum of Electromagnetic Fields: Spin-3/2 Light. O. El Gawhary, T. Van Mechelen, and H. P. Urbach. Phys. ...
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29 views

Amplitudes of the $B$ fields? [closed]

the question is What are the amplitudes of the B fields associated with the following equations (1) and (2)? $$(\omega^2 - \omega_p^2)E_{\parallel} = 0 \: \Rightarrow \omega^2 = \omega_p^2 \...
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1answer
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Do Electromagnetic waves exert equal force on positive and negative charges?

Waves in the Electromagnetic fields propagate with the speed of light and have perpendicular E- and B-components. These components should exert a Lorentz force on a charged particle that exists in the ...
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Microwave interaction with a beamsplitter

A few questions here, but some background first. I've borrowed some microwave emitters from my school's physics department, but for the experiment I'm trying to perform I need to split a beam. This ...
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1answer
37 views

Divergence of Lienard Wiechert E-Field is not zero? (Violation of Gauss' law)

I wanted to see if the divergence of the lienard wiechert field follows Maxwell's equations (gauss' law): $$\nabla \cdot \vec{E} = 0$$ for $$ E(r,t)=\frac{e}{\gamma^2 R^2} \frac{n-\beta}{(1-n\cdot\...
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1answer
34 views

Total internal reflection of sine wave vs smooth step function [closed]

If an electric field described by the function $$f(t)= \begin{cases} 0&\text{if}\ t<0\\ \sin(t)&\text{if}\ 0\leq t\leq \frac\pi2\\ \ 1&\text{if}\ t>\frac\pi2 \end{cases}$$ ...
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1answer
27 views

On contraction, aberration and redshift of light from a mirror for an observer who remains still

Last week I came across with a question from an old course I took in General Relativity which said this: Suppose you are traveling at speed v=0.9c respect to an observer who remains standing up still ...
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2answers
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How is it possible that the earth has the concept of energy equilibrium: the same amount of energy comes in and out?

I was reading this article on the Earth's Energy Budget, as well as a few other articles that basically contained the same information: That there must be an equilibrium of energy coming into the ...
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2answers
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Probabilistic interpretation of Malus's law

A beam of photons is polarized in the vertical direction. What is the probability that a photon will pass two filters, the first at $45^{\circ}$ and the other at $75^{\circ}$? The answer is given by $...
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3answers
55 views

Can a lens be used at radio frequency?

Lenses and Antennas are two means of manipulating EM waves. While antennas are predominantly used at RF / Microwave frequencies, Lenses are used for optical/IR regions of the spectrum. I understand ...
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0answers
24 views

Energy of light rays under First Law of Thermodynamics [duplicate]

There is increase in the wavelength of light from distant quasars as it reaches us, due to the constant expansion of the Universe, or so I understand. In that case, due to increase in wavelength, the ...
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3answers
97 views

EM waves and cable shields

After reading about cable screens to prevent electric field interference such as: “Most of our audio cables are screened, and this does a decent job in keeping the Radio Frequencies at bay, but ...
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0answers
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How can we see through the matter like glass [duplicate]

I have a very peculiar question. We have some categories of substances like transparent, opaque, translucent. My question is when it comes to transparent objects like glass which is solid, how can we ...
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1answer
30 views

Li-Fi versus Wi-Fi for underwater communications

One of the main advantages of Li-Fi over Wi-Fi that is often stated in journals is that Li-Fi works underwater while Wi-Fi does not. But the frequency of visible light is much higher than the ...
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1answer
30 views

How to obtain the luminosity of a blackbody disk? [closed]

How do I get the luminosity of blackbody disk (negligible thickness) with temperature $T$ and radius $r$? Also how can one obtain the flux density if the object is at a distance $d$ and an ...
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1answer
33 views

Using Stokes parameters, how do I quantify the co-polarization and cross-polarization?

Given the Stokes Vector $$S_i = I_0\begin{pmatrix} 1 \\ 0.6 \\ -0.2 \\ 0.07 \end{pmatrix}$$ how do I quantify the polarization? Is there a way to say $S_i$ is $x$% right- or left-hand-circular, $y$%...
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2answers
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What determines the timescale for fluctuations in the electromagnetic field from a light source?

Let's say you place an electric field meter some distance from a light bulb. As a function of time the output of the meter would be $\mathbf{E}(t)$. I would guess that the electric field will be some ...
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0answers
36 views

Electromagnetic waves, Electromagnetic theory

My school book says "according to classical Electromagnetic theory, an accelerating charged particle emits radiation in the form of Electromagnetic waves and the frequency of the Electromagnetic waves ...
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1answer
19 views

What happens at an atomic level that allows us to see objects that are only in the same order of magnitude as visible light's wavelength?

By virtue, humans eye can only see EM wave in the visible light region. From my understanding of 'why we see things', it is because light reflect off an object and the lights' diffraction patterns ...
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0answers
26 views

What is the correct way to calculate the intensity of an electromagnetic wave?

I am looking for some clarification on how the intensity of an electromagnetic wave is calculated at a point. For simplicity, let's only consider waves at a single frequency, in one direction. An ...
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2answers
42 views

What makes the disturbance in Electromagnetic waves move.?

I get that changing electric field will have a curly changing magnetic field and changing magnetic field will have curly changing electric field. So when we move a charge up and down, electric field ...
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0answers
26 views

Can light of different frequencies interfere with each other?

In principle I'm aware of superposition and how it works. Nevertheless I'm not really able to answer the following: Will two light beams of different frequencies interfere with each other? More ...
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24 views

In a transparent medium what does it mean if the group index is increasing?

I am new to Photonics and I lack the intuitive understanding about group indices and group velocities. I know group velocity is the velocity of the pulse in the medium. Does it mean that it is the ...
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4answers
86 views

Is the vacuum permittivity a result of defining other units first?

From Coulomb's law $$F=\frac{1}{4\pi\epsilon_0}\frac{q_1q_2}{r^2}$$ If instead we defined the charge of a coulomb to be $\sqrt{\epsilon_0}$ times it is now, the force would be exactly the ...
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14 views

Glint effect in electromagnetic waves

Two plane waves having the same frequency and different intensities: $$E_0=Ae^{i(\omega t-kr_0)}$$ and $$E_1=Be^{i(\omega t-kr_1)}$$ arrive at point $P=(x,y)$ from two point sources located at a ...
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0answers
19 views

Does a high-velocity ion being neutralized by an electron emit Brehmsstrahlung radiation?

I'm curious about a point of the physics of Polywell electrostatic confinement fusion devices. One of the key claims made in the design is that by confining some "low temperature" electrons to a ...
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0answers
22 views

Wave Equations from Decoupling Maxwell's Equations in Bianisotropic Media

For several days now, I have been trying to decouple Maxwell's equations in bianisotropic media so that I end up with a form that involves only one variable (of E, D, B, H), i.e. a so-called 'wave ...
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2answers
38 views

Which Fresnel coefficients should be used at normal incidence?

There are two sets of Fresnel coefficients depending on the polarisation of the incident light. At normal incidence these equations converge except there is a phase factor of $\pm1$ For the reflection ...
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2answers
114 views

Do electromagnetic fields have inertia? Or, what sets the speed of light?

In all mechanical waves, there is a restoring force and an inertial influence. For example, a plucked string oscillates because the restoring force brings it back to being straight and then the string'...
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2answers
54 views

How can Line of Sight work?

How can a mobile phone work inside a closed room with no openings if Line of Sight requires no obstacles between the receiver and transmitters? I know you may think it's not a Physics question but ...
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1answer
29 views

What would be the material properties of a perfect reflector?

If I want to model a perfect reflecting material, what material parameters should I use? Specifically what refractive index or dielectric constant should I use? I know from the Fresnel equations that ...
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0answers
17 views

Optical tweezers : dipole force or radiative pressure?

Two types of forces are usually considered to describe light-matter interaction. On the one hand, the radiative pressure, which corresponds to absorption - spontaneous emission cycles, is proportional ...
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2answers
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Why is the downward transition of electrons in a three level pumping scheme of laser non radiative?

Laser produces coherant monochromatic waves by stimulated emission of radiation. In the three level pumping scheme of laser the downward transition of electrons from E3 to E2 is spontaneous and from ...
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2answers
67 views

Reflection and transmission of general electromagnetic wave

Given is a source $S$ which produces an electromagnetic wave $E(x,y,z)$. The source is in vacuum. At z=0 there is an interface between vacuum and a perfect dielectric with $\epsilon$. The electric ...
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2answers
91 views

Does light have a non-zero mass? [duplicate]

I heard that the light has zero mass. But I searched in internet, some people say light has mass and some people said doesn't. I am not sure what is the right answer. And also I heard that the reason ...
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1answer
39 views

Equation of an electric field of a Gaussian pulse

I am trying to write the equation of electric field of a Gaussian pulse of light to do some MATLAB analysis and other analysis. What I want is an electric field $E(y,t)$ of a Gaussian pulse traveling ...
2
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1answer
48 views

How does polaroid filter work at the atomic level? [duplicate]

I know it works by blocking electric or magnetic component of wave while allowing other but what happens at the atomic level , do the atoms absorb the electric component e.g by excitation of electrons ...
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4answers
94 views

Can Fourier transform be applied to light, as a way to find the individual elements of a color?

The Fourier transform can help one discern the individual frequencies of a sound. Every sound can be decomposed into sine waves. Knowing that light is a wave, that it "has" a frequency, is it ...
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1answer
83 views

How to solve the wave equation? [closed]

The solution of classical wave equation $$\nabla^2\textbf{A}=\frac{1}{c^2}\frac{\partial^2\textbf{A}}{\partial t^2}$$ is $$\textbf{A}(r,t)=\textbf{A}_0(e^{i(\textbf{k}\cdot\textbf{r}-wt)}+e^{-i(\...
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0answers
26 views

Is infrared active phonon the reason why infrared is not passing through walls?

I did some research on why infrared is not passing through walls.I learnt about infrared active phonons which are responsible for scattering in solids.It cannot be raman scattering,rayleigh scattering,...