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

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Is the Speed of Light an universal spacetime constant, the velocity of electromagnetic waves, or of photons?

This question has been touched tangentially by What's a better phrase than "speed of light" for the universal spacetime speed constant? and Could light travel more slowly than the ...
2
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1answer
2k views

Physical meaning of Maxwell's equations and origin of EM waves

Is it possible to describe the physical meaning of Maxwell's equations and show how they lead to electromagnetic wave, with little involvement of mathematics ?
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2answers
403 views

What is the difference between light and visible light? [duplicate]

After watching a few videos on light and electromagnetic radiation, I am a little confused. The way things are explained, is that light is just the same as electromagnetic radiation I thought this ...
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2answers
539 views

Do x-rays and gamma rays also contain photons like visible light does?

Do x-rays and gamma rays also contain photons like visible light does? If so, then what makes photons of visible light and other waves different? The rest mass of a photon is zero, but as it moves at ...
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3answers
2k views

Temperature behavior over time of black or white cars in hot, sunny regions

How does the color of a car influence its inner temperature change over time when parked outside in windless, hot and sunny regions? I know what's the common idea about that: black cars are supposed ...
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2answers
355 views

Why doesn't the magnetic field polarize when polarizing light?

If the magnetic field doesn't polarize does it follow the electric field path of propagation? or does it vanish?
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3answers
3k views

Why is it necessary for an object to have a bigger size than the wavelength of light in order for us to see it?

I keep hearing this rule that an object must have a bigger size than the wavelength of light in order for us to see it, and though I don't have any professional relationship with physics, I want to ...
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2answers
77 views

On the shape of magnetic and electric fields in an electromagnetic wave

Electromagnetic waves are generally depicted like this: Where the electric fields and magnetic fields exist in the planes perpendicular to the direction of propagation. I also realize that as the ...
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1answer
87 views

Would white light waves act as same as monochromatic waves in double slit experiment?

Would white light waves act as same as monochromatic waves in double slit experiment? If not, what pattern would be seen on the screen?
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1answer
88 views

AM vs FM radio under bridges

I know what the difference between AM (Amplitude Modulation) and FM (Frequency Modulation) radios is. However, I noticed that when I drive under a bridge while listening to a station on AM, it just ...
2
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2answers
108 views

Would it be possible to detect nuclear explosion on exoplanet?

How strong would have to be nuclear explosion on exo-planet that orbits some other star for it to be detectable outside of that system. Or it would be impossible due to amount of radiation coming from ...
0
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1answer
125 views

Electromagnetic radiation and black body radiation

I was taught today that the Electromagnetic wave Theory is unable to explain black body radiation. The example that was given to me: When a metal is heated, it emits different frequencies of light as ...
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1answer
85 views

Is the body's exposure to an x-ray equal to an airplane trip across the country?

I have heard numerous times when getting x-rays, MRIs, CAT Scans, etc. that each one is equivalent to a cross country airplane trip. Disregarding the different types of radiation as asked in this ...
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4answers
867 views

Magnetic fields and gravitational waves. How far do they reach?

I read that magnetic fields perpendicular to a current shoot out and expand all the way to infinity. Additionally a gravitational wave, no matter how small will also expand to infinity at the velocity ...
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3answers
789 views

Why aren't all photons virtual particles even in the “vacuum” of empty space? [duplicate]

I'm thoroughly confused about the nature of electromagnetic radiation. Light is supposed to exhibit both wave and particle characteristics. But does that mean that it is both a wave and a particle or ...
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4answers
846 views

Can an LC oscillator be used to generate visible light?

The LC oscillator is most commonly used to generate radio waves for practical use and the frequency $\omega$ of the LC oscillator equals that of the electromagnetic wave so produced. So, can they in ...
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1answer
51 views

Why 21cm line observations is more helpful compared to other radiation?

Why 21cm line observations is more helpful compared to other radiation? Is it only because of its abundance in whole universe or anything else?
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3answers
176 views

Should a Faraday cage block a radio's signal?

Today, I tried creating a very basic Faraday cage by surrounding a radio with two baking trays made out of iron. It didn't seem to affect the radio's signal (AM was being used, not FM). In theory, ...
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3answers
3k views

How much electric charge do electromagnetic waves carry?

Since electromagnetic waves have both electric and magnetic field components, which oscillate in phase perpendicular to each other and perpendicular to the direction of energy propagation. How much is ...
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0answers
689 views

What happens with photon when it is slowed down substantially?

In a dispersive media light's velocity can change substantially. Imagine we can slow it down to near 0 what the wave would look like? Frequency of light does not seem to change even at v=0 (at least ...
5
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1answer
62 views

Question on luminosity of a radiant source and its dependence on temperature, and involvement of Doppler Effect

A few days ago, I happened to go through the chapters on Radiation, and Photometry, studying them at quite an elementary level. I studied Wien's displacement law, and the dependence of luminous flux ...
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2answers
43 views

optical diffusion (scattering) versus refraction

When an electromagnetic wave meets an interface a part of it is reflected and part of it is refracted (and from the refractive index I can calculate the angles of propagation and the intensities using ...
8
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2answers
561 views

Do gravitational waves slow down as they pass through matter?

I've heard that gravitational waves travel at the speed of light, and have some parallels to electromagnetic waves. EM waves slow down as they pass through matter (speed of light in glass is slower ...
5
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1answer
121 views

Do radio waves travel around the Earth or through it?

Whenever you hear someone illustrating/describing the transmission of radio waves they always make it seem like they'd travel perfectly around the Earth to another distant location. For example, a ...
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2answers
147 views

Is it possible to have a perfectly black material?

After reading this NASA article about the "blackest material", the following stuck out to me. The tiny gaps between the tubes absorb 99.5 percent of the light that hits them Is it possible to ...
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3answers
326 views

What makes Poynting's theorem consistent for a charge moving in a static electric field?

Poynting's theorem is given by $$\frac{\partial}{\partial t}\int_{v}Udv + \oint_{A}\vec S\cdot \vec {dA} +\int_{v}\vec E\cdot\vec J dv =0 $$ Where, the total electromagnetic energy inside the ...
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0answers
44 views

Confused about SI and CGS Units For E/M Energy

I've been looking at some papers on wakefields of electron beams and I am a little confuded about the units. They do not specify whether or not they are in cgs or SI units. Here is a sample equation: ...
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2answers
4k views

How to determine directions of vectors of an electromagnetic wave

I did an exercise which probably is quite popular, in which you draw an electromagnetic wave and prove that it should propagate at the speed of light $1 \over \sqrt {\mu_0\epsilon_0}$ using Farday's ...
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4answers
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Can a photon get emitted without a receiver?

It is generally agreed upon that electromagnetic waves from an emitter does not have to connect to a receiver, but how can we be sure this is a fact? The problem is that we can never observe non ...
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0answers
19 views

Understanding What A Wakefield Describes?

I am trying to understand the some of the properties of wakefields, namely the energy change. So, as a preface I am interested in primarily the wakefield due to electron beams as they progress through ...
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5answers
4k views

Can the sun cast a shadow?

The sun's light can cast the shadow of another object, but does it ever cast its own shadow?
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3answers
471 views

Curl of an electromagnetic wave?

I can't understand the concept of the curl of an electromagnetic wave. $$ \nabla \times E = -\frac{\partial \textbf{B}}{\partial t} $$ All of the examples I find show a current through a conductor, ...
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1answer
20 views

How does intensity differ from apparent luminosity in the context of photometry?

Context: photometry in astronomy. Background: The total luminosity $L$ of a star is the energy that radiates in all spatial directions in all wavelengths and is given by the following formula, where ...
0
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1answer
53 views

Electromagnetic waves and group velocity

I have three questions about electromagnetic waves and was wondering whether anybody here could comment on these things: Wikipedia says that there are no longitudinal EM waves, although TM and TE ...
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1answer
73 views

Constructive Interference of Electromagnetic Waves

So I was wondering if Electromagnetic wave has the same property of interference as normal waves. I understand that both the electric and magnetic parts of the wave would have to be in the same ...
11
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2answers
4k views

How does reflection work?

In Newton's model of light as being composed of particles, it's easy to imagine reflection as being the rebounding of individual corpuscles off a surface. However, since light can also behave like a ...
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1answer
76 views

What does it mean for an electromagnetic structure to be resonant?

There are many electromagnetic structures used in microwave engineering and EM devices. For example, patch antennas, metamaterials made from unit cells, etc. When they design structures like patch ...
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1answer
32 views

Increasing Earth's albedo

How much of a difference would it make if every roof, road and vehicle were painted white? This would certainly reduce the urban heat island effect but how much of a difference would it make to total ...
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1answer
28 views

is it possible to change the energy of a waveform like radio wave & turn it into microwave?

In the electromagnetic spectrum, the differences between all waveforms are the "frequency" & energy of the waveform. We are able to modify both of these parameters. So, is it possible to change ...
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1answer
47 views

Mathematical Formulation for Accelerating Charges Generating Light?

I haven't been formally taught the fact that accelerating charges generate light, and I have seen the picture of an accelerating charge sending ripples down its field lines, but is there a ...
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1answer
740 views

Why is there a photon every millimeter on earth coming from a star millions of light years away?

I've been having this confusing thought for so long now it would be amazing if someone could answer me. Imagine this asterisk * . As you see, from the center point, lines go outwards, just like a ...
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1answer
34 views

Excited Energy levels of Hydrogen vs Solids

My question has to do with Excited Energy Levels. I keep reading and learning that all objects/most solids emit infrared radiation. But to emit radiation, an object's particles must first enter a ...
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4answers
231 views

Why can x-rays pass and not radio waves?

If we stand in an elevator or other metal containers we lose radio signals etc the very same reason for which we cannot see across a block of metal that light cannot penetrate it. However x-rays and ...
14
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2answers
381 views

Do accelerated charges radiate or not?

This questions has been asked all over the net (here included) but I can't find a satisfactory answer or discussion. Some say it does not radiate if the acceleration is caused by a uniform gravity ...
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1answer
58 views

Electromagnetic wave in a medium with $\sigma \ne 0$ [closed]

I want to prove that the reflectancy of an Electromagnetic wave in a medium with $\sigma$ $\ne$ 0 is: \begin{align*} R_{\|}=R_{\perp}=\frac{(n-1)^2+k^2}{(n+1)^2+k^2} \end{align*} any advice, please? ...
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0answers
48 views

Can temperature affect or change the wavelength or frequency of EMR?

If we were to emit Electro Magnetic Radiation(X-rays for example) to a very hot body such as the sun would we still get X-rays if we had a capturing device at the other end or would the high ...
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4answers
441 views

Does Light Experience Length Contraction?

Lorentz length contractions states that the length of any moving object gets divided by the Lorentz factor equal to the Lorentz factor for that object (always $\geq 1$), equal to $$ ...
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1answer
43 views

How is Transition Radiation different from EM waves crossing a boundary?

Just confused my self again :(. Transition radiation is the radiation produced when a charge crosses a boundary between two dielectric materials (http://en.wikipedia.org/wiki/Transition_radiation). As ...
5
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1answer
233 views

Is the number of wavelengths of light spanning a distance invariant with respect to spacetime distortion?

I was recently asked by a friend how the expansion of spacetime affects photons. I gave him what I feel is a satisfactory general response, but it got me wondering how, exactly to calculate this ...
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2answers
993 views

Why electrons can't radiate in their atoms' orbits?

It's an old-new question (I found only one similar question with unsatisfactory (for me) answer: Where did Schrödinger solve the radiating problem of Bohr's model?) It's strange for me how all books ...