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

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Electromagnetic radiation lenses

This will probably be a very basic question, but looking for a simple answers. What I know the visible light is a form of electromagnetic radiation with a defined wavelength. the full spectrum ...
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0answers
22 views

Why is radiation at the relativistic limit characterized by 1/gamma angle?

Trying to think of a reason as to why? Also, the factor that radiation is zero on axis? I haven't been able to resolve these two fundamental principles in my head :(
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6answers
1k views

What causes polarised materials to change colour under stress?

Our physics teacher showed the class a really interesting demonstration. He used two polarised filters in opposite orientations, then he took some antistatic tape and stretched it under the two ...
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1answer
39 views

What is the physical significane of Complex Time Evolution in EM Waves? [duplicate]

So, I have been having a hard time understanding why there is even a complex phase for EM waves: $$\phi=\exp[i\omega t]=\cos(\omega t)+i\sin(\omega t)$$ Don't understand why it is there? Any one ...
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6answers
3k views

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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2answers
98 views

How to show with Maxwells Equations that nonaccelerating charges dont radiate? [closed]

How to show with Maxwells Equations that nonaccelerating charges don't radiate?
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3answers
298 views

Comparing predictions and reality for the gravitational attraction due to light beams

While doing some on-the-side reading, I stumbled across this question: Do two beams of light attract each other in general theory of relativity?. Great question and a great, easily understandable ...
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1answer
60 views

Why are radio waves in the 1.43 - 2.5 Mhz range invisible?

Visible light diapason is 400 - 700 nm which is 1.43 - 2.5 Mhz. If using an antenna I would broadcast steady sinusoidal wave in this range, why the EM emitted by the antenna are not visible? Suppose ...
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1answer
105 views

What really is reflection? [duplicate]

What really is reflection? Is it just the reemission of EMR? I asked my teacher, he said in quantum sense, it is true. But when I read something about emissivity in Stefan Boltzmann's equation, it ...
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6answers
9k views

Why glass is transparent?

Once I asked this question from my teacher and he replied "because it passes light", "and why it passes light" I asked and he said "because it is transparent". Same question again, Why glass is ...
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3answers
2k views

Intensity of light

If we have 2 beams of light with equal intensities, but with different frequencies, wouldn't the one with the higher frequency generate more power? If so, how come the intensity, which is in $W/m^2$, ...
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3answers
2k views

How to calculate gamma radiation shielding?

A device emits 0.2 μSv/h of gamma rays. How thick does an aluminum sheet need to be to completely stop radiation from coming out ? What equation is to be used to calculate this ?
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1answer
70 views

Waveguides Transmission Mode Determination

How do I know if I have TE, TM, or TEM rectangular conductive waveguide? For instance, I am doing a lab where we want maximum magnetic field in the waveguide, does that mean we want the TE because ...
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1answer
129 views

Soft Bremsstrahlung: why $\hat{k}\cdot\mathbf{v}= \mathbf{v}'\cdot\mathbf{v}$?

On page 181 in Peskin & Schroeder they say that we consider the integral (intensity) $$\tag{1}\mathcal{I}(\mathbf{v},\mathbf{v}') = ...
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0answers
22 views

Detailed balance formulation in solar cells?

Hello I wanted to know where does the integral of following picture come from and what are the alternatives in it? How and where can i find information i need to know to understand this text? thank ...
18
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4answers
2k views

Newton's rings: What causes the other rings?

This is from an experiment we did in physics class. We shone a sodium light at a convex lens on top of a sheet of glass - and this image was captured by a USB microscope. I know what causes the main ...
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1answer
71 views

Difference between Cotton Mouton effect and inverse Cotton Mouton effect

The Cotton mouton effect is observed when a linearly polarized electromagnetic wave passes through a dielectric medium and a magnetic field is applied perpendicular to the direction of propagation of ...
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2answers
196 views

Why aren't solar panels efficient?

Why can't solar panels produce 1 Kw per 1 square meter? This is the energy of the Sun's radiation per square meter on Earth but solar panels don't come close. Why can't we trap all that energy? ...
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1answer
62 views

Why electric field has a major role in vision?

Although the electromagnetic wave is made op of both electric and magnetic fields the electric field contributes much in vision and is thus, called the light vector. But, why is it that the electric ...
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2answers
232 views

Do photons and cosmic rays radiate energy through gravitational waves? If not, why not?

Due to the mass-energy equivalence, both matter and EM radiation bend spacetime, and both are capable of forming singularities (black hole, white hole/kugelblitz). In light of this, why do photons ...
43
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7answers
4k views

Cyclist's electrical tingling under power lines

It's been happening to me for years. I finally decided to ask users who are better with "practical physics" when I was told that my experience – that I am going to describe momentarily – prove that I ...
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3answers
1k views

Why does a human body only emit infra red radiation and not other types of electromagnetic radiation?

What causes humans to emit infra red radiation and why don't we also emit other types of electromagnetic radiation such as ultra violet or microwave? Sunlight contains UV and our body takes it in, but ...
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1answer
85 views

Why polarization vector $= (0,1,i,0)$?

I know from CED that one has e.g. polarization $$\vec{E}(z,t) = \begin{bmatrix} e_{x} \\ e_{y} \\ 0 \end{bmatrix} \; e^{i(kz - 2 \pi f t)}. $$ Why do Peskin&Schroeder define a polarization ...
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1answer
177 views

Orbital angular momentum of photon

People talk about orbital angular momentum (OAM) of photons. Is there some physical example that cannot be explained without assuming that photons have non-zero OAM? Does different photons have ...
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2answers
84 views

Do acousto-optic modulators shift the frequency of the diffracted beams?

Today I read an introduction on an optical device called an acousto-optic modulator, which is used in many optical experiments. It is the first time I have heard of this element. The material showed ...
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1answer
273 views

Faraday rotation effect in circularly polarized waves?

We all know farady effect is observed in linearly polarized wave when it passes through a dielectric medium and magnetic field is along the direction of propagation. Is this phenomenon observable in ...
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1answer
113 views

Can atmospheric pressure literally push electromagnetic waves?

I work for an IT company and some time ago we had an issue with our wireless internet. We are 5 miles away from the ISP's antenna. Our Sys Admin expressed the view that the electromagnetic waves are ...
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1answer
1k views

What IS reflection?

How does quantum electrodynamics actually explain HOW reflection occurs on a microscopic scale? Note that Feynman's QED lecture series/book is not sufficient, as he only assumes that light DOES ...
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1answer
77 views

How does a MRI use 20.1kW yet creates over 204K BTU/h? [closed]

I've been reading through a manual about MRI operating procedures for a large healthcare provider. The manual (written by Siemens) states that the MRI machines use 9kW in stand-by mode and 20.1kW ...
4
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1answer
182 views

Does the cavity magnetron in a microwave oven produce x-rays?

It seems like it should due to bremsstrahlung, since we're talking about electrons with 5-7KeV of energy slamming into the walls of the device, but I've found no information about this online, so I'm ...
28
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4answers
2k views

Do two beams of light attract each other in general theory of relativity?

In general relativity, light is subject to gravitational pull. Does light generate gravitational pull, and do two beams of light attract each other?
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0answers
68 views

Dynamic light scattering of rods at low q

In dynamic light scattering (DLS), I understand that for spherical particles it is their diffusive motions which cause the intensity fluctuations that are correlated. And that the scattering vector ...
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1answer
81 views

Can an EM wave be represented in terms of dipole?

The direction of propagation is represented by a line. A positive charge moves along this line at velocity c. A negative charge moves along a line that is perpendicular to the direction of propagation ...
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2answers
699 views

Why does noise affect FM radio less than AM?

Frequency modulated waves are less susceptible to noise compared to amplitude modulated signal. This is because the information in an FM signal is transmitted through varying the frequency, and not ...
6
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2answers
187 views

Multiple channels of information in single electromagnetic wave?

I'm trying to understand how can multiple radio stations transmit information just by transmitting using different frequency. The way I understand it all those different frequency waves add up to a ...
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4answers
119 views

Why does special relativity talk about the speed of light in a vacuum?

What's the importance of the speed of light being in a vacuum? Does not being in a vacuum cause a difference?
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1answer
427 views

Can electron exist as a standing wave inspite of successive superposition?

With the development of quantum mechanics, it was found that the orbiting electrons around a nucleus could not be fully described as particles, but needed to be explained by the wave-particle duality. ...
6
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2answers
5k views

How & Why does accelerating charges radiate electromagnetic radiation?

Lets consider it case by case: Case 1: Charge particle is at rest. It has electric field around it. No problem. That is its property. Case 2: Charge particle started moving (its accelerating). We ...
21
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12answers
23k views

Why is light called an 'electromagnetic wave' if it's neither electric nor magnetic?

How can light be called electromagnetic if it doesn't appear to be electric nor magnetic? If I go out to the sunlight, magnets aren't affected (or don't seem to be). And there is no transfer of ...
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2answers
101 views

Geiger meter affected by plasma lamp

Whilst testing a geiger meter I took it near a plasma globe (the type sold in party/toy stores). The meter showed 0.13 mcSv/h. Then I turned the lamp on and low and behold the meter jumped to 0.89 ...
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1answer
45 views

Why does black get heated the most? [duplicate]

I found out black heats up the most and white the least, as I expected. The question I had is that despite black reflecting all the wavelengths of the visible spectrum, and hence giving the black ...
33
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4answers
2k views

Scattering of light by light: experimental status

Scattering of light by light does not occur in the solutions of Maxwell's equations (since they are linear and EM waves obey superposition), but it is a prediction of QED (the most significant Feynman ...
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1answer
92 views

Why can TV broadcasts send such large amounts of data(photorealism) and a PC cant

Firstly I think I am right in saying that TV broadcast are sent via electromagnetic waves which means they are sent via photons, how is that even possible? And then the main questions, how can you ...
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0answers
50 views

Spatial light modulation for mode multiplexing, how does it work?

If a laser light becomes spatial phase modulated (by phase only spatial light modulator) what happens to the intensity distribution and frequency spectrum of the laser light ? I know that this ...
9
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3answers
626 views

Do particle accelerators produce (dangerous) radiation?

I was under the impression that particle accelerators were pretty harmless, but some article said that they produce harmful radiation when you're in the tunnel. Given that the Internet... isn't always ...
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2answers
620 views

Why do electromagnetic waves oscillate?

I've been considering this question, and found many people asking the same (or something similar) online, but none of the answers seemed to address the core point or at least I wasn't able to make ...
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2answers
132 views

What would give us more heat ? infrared or microwaves?

As we know that our body is made up mostly of water and the frequency of vibration of water molecules matches that of microwaves which is the working principle of microwave ovens. When we come in ...
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2answers
239 views

Why do waves diffract?

There have already been a lot of questions on this site on diffraction but I still believe this one might be slightly different. In electromagnetic waves, diffraction and any other phenomenon of wave ...
5
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3answers
2k views

What happens to light in a perfect reflective sphere?

Let's say you have the ability to shine some light into a perfectly round sphere and the sphere's interior surface was perfectly smooth and reflective and there was no way for the light to escape. If ...
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0answers
68 views

Do I understand measurement of dispersion relation in a solid correctly?

I'm currently doing an introduction to solid state physics course and have a quick question about measurement of the dispersion relation of phonons in a solid: The way I understood it is the ...