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

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138 views

How to calculate loss due to Gaussian beam divergence of a laser going through multiple lenses?

To better explain my question, I will need to give a brief description of the configuration used in 2D MEMS switches. So, the next figure shows a configuration of a 2D MEMS switch, a light beam ...
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2answers
147 views

Is my simulation result for unpolarized light correct?

This is a follow-up of this question. After that, I picked up some knowledge of FDTD (an algorithm for solving Maxwell's equations) and simulated following scene: Pic 1 As the picture shows, a ...
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1answer
31 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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2answers
270 views

Why does the light travel slower in denser medium? [duplicate]

Wikipedia says that "in general, the refractive index of a glass increases with its density." And the refraction index of water vapor is less than ice, and even less than liquid water. Is there any ...
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3answers
168 views

How could electromagnetic waves propagate through space although they have no electrons?

How could electric fields in these waves propagate through space although in space there's no electrons for the electric field to be formed? is there another type of charged particles that carry the ...
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0answers
42 views

Why in 2+1 spacetime dimensions electromagnetic wave (light) cannot be distinguished with acoustic wave (mechanical wave)?

I have heard a saying that in 2+1 spacetime dimensions electromagnetic wave cannot be distinguished with acoustic wave. Or maybe they want to say in 2+1 spacetime dimensions photon and phonon cannot ...
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1answer
130 views

How does the Cosmic Microwave Background give us information about the Big Bang?

I was reading about CMB after this new breakthrough last week and I could not figure this out. The CMB did not exist before the epoch of Last Scattering. They were just photons which were formed at ...
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19 views

How to compute radiated power from known instantaneous potential distribution

Friend of mine has a device that has an oscillating electric potential and he wants to know how much power it radiates. He can simulate the instantaneous electric potential using a software package, ...
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1answer
73 views

Why is titanium dioxide transparent for visible light but not for UV?

I wonder the reason for TiO2 thin films to be transparent for visible light but not for UV. I made a quick search and I found that it is due to the band gap of TiO2. It absorbs UV light but not ...
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1answer
96 views

Is every electromagnetic radiation considered “light”?

Somebody mentioned on Freenode chatroom for physics that All Electromagnetic Radiation are delivered in form of Photons not just light. Is it true? Does that mean if we get a THF electrical ...
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2answers
96 views

Can electromagnetic fields be used to shield electromagnetic radiation?

Can electromagnetic fields be used as shielding for electromagnetic radiation?
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2answers
54 views

EM Radiation and Heat

If there is EM radiation, will there always be a heat exchange between the wave and its surroundings? If you have an extremely energy-efficient light bulb that converts ALL the energy it receives into ...
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1answer
143 views

Write down equations for the electric field and magnetic fields components of a linearly polarized plane wave [closed]

A linearly polarized plane wave at 100 MHz is propagating in the $z$ direction. The electric field vector makes an angle of 30° with the $x$-axis. Its peaks amplitude is measured to be ...
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1answer
58 views

Could an attachment to cell-phones limit or neutralize electro-magnetic radiation?

Assumption: Cell-phones generate some degree of electro-magnetic radiation. Whether it's harmful or not is not the question here. Claim: Certain devices may "neutralize" this radiation. (Ex: ...
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41 views

Primordial black hole: how dense does matter need to be to feed it?

Primordial black holes are a dark matter candidate. Suppose you put a primordial black hole the mass of an asteroid in Earth's core. Will it grow? NO! The black hole will be on the order of a proton ...
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3answers
105 views

What is radiation(in simple words)? [closed]

I am a student who is interested in scientific facts. I want a simple definition for radiation. Neither too scientific, nor too simple.
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3answers
682 views

Prove EM Waves Are Transverse In Nature

Why we say that EM waves are transverse in nature? I have seen some proofs regarding my question but they all calculate flux through imaginary cube. Here is My REAL problem that I can't here imagine ...
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1answer
49 views

phase difference between incident plane wave incident on a dipole and radiation fields from dipole

i have an incident plane wave and a dipole, consider that plane wave incident on dipole. at this moment what happen for dipole ? we know that after incident of plane wave on dipole, the radiation have ...
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0answers
88 views

How is extremely low frequency (ELF) radiation collected by a submarine antenna?

The U.S. Navy Project ELF managed to generate extremely low frequency (ELF) radiation at down to $\approx 76$ Hz (implying a wavelength of $\approx 3,945$ km!). I was curious, what kind of receiving ...
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34 views

Would electron degenerate matter be a good x-ray reflector?

I do not know much about x-ray physics or degenerate matter, but I have the intuitive feeling that the high electron density and what must be some crazy band structures in electron degenerate matter ...
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0answers
19 views

Building a magnetron powered steamer

I am wanting to build a microwave powered steamer for a reverse engineering project in university. I've read up some on this and know that its not as efficient as a heating element. I'm curious about ...
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2answers
103 views

Why doesn't alternating current produce light while a vibrating single particle with a charge will

If a vibrating atom can produce light why can't an alternating current of electrons do the same? EDIT: When I use the term "light" I mean all EMR
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3answers
88 views

Do photons interact only with single particles or can a single photon be absorbed by 2 or more particles simultaneously?

Say I have 100 particles in a vacuum that are spread out such that their movement caused by a time variant electromagnetic field does not have an effect on each other. That is the particles can not ...
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33 views

Electron and photon interaction

Assuming I shoot a beam of light to an electron, the electron will take the energy and reemit EMR at all direction randomly? If it will, is it happening at the same time?
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1answer
69 views

Could the Sun be partly powered by cosmic rays?

The Earth and the Sun has magnetic fields which shields us from cosmic rays, as a charged cosmic ray particle will loose kinetic energy when its direction is perpendicular to the magnetic field. So ...
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1answer
62 views

black body radiation graph [duplicate]

I got really confused about the graph of the relationship between wavelength and intensity of black body radiation. What does the peak stand for? And what does the graph tell us?How can we analyze it? ...
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1answer
50 views

What is the theoretical wattage output of a Tokamak fusion reactor?

By that I mean the complete radiative wattage of any type of energetic radioactivity or electromagnetic wave or even particle if that's what they output. My purpose is to compare this to the suns ...
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1answer
43 views

Why is radiation for an ultrarelativistic charge zero on axis?

I attribute it to the fact that for an ultrarelativistic charge the field is contracted and essentially there are only fields in the transverse direction and nothing longitudinally (wrt the charges ...
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0answers
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Where does 1/Gamma characteristic angle come from in EM Radiation?

Very curious as to where this angle comes from? It describes the peak of radiation for almost all radiation regimes, but I am having a difficult time seeing where it comes from. Also, the physical ...
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8answers
9k views

Why does a remote car key work when held to your head/body?

I was trying to unlock my car, but I was out of range. A friend of mine said that I have to hold the transmitter next to my head. It worked, so I tried the following later that day: Walked away from ...
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1answer
82 views

Deriving and gaining intuition for the equation for the index of refraction $n = \sqrt{\mu_r\epsilon_r}$

I've come across the equation in the title. It relates the index of refraction of a substance to the square root of the product of the relative permittivity and the relative permeability at whatever ...
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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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1answer
56 views

Far Field Diffraction of EM waves: what does the zero frequency signify?

If you have a system of independently radiating electrons/point-charges, the far field distribution of the EM waves can be approximated by the fraunhoffer diffraction integral, or simply by the ...
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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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3answers
4k views

Is it possible to avoid the radiation that caused the American flag turned into white on the Moon? [closed]

While lunar images have proven that the American flags planted during the Apollo missions are still standing on the moon, lunar scientists have now said that they probably no longer hold the iconic ...
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1answer
42 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 ...
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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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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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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
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
54 views

Electromagnetic spectrum

I understand that the electromagnetic spectrum is made up of different frequencies of light waves, but is this true in all cases such as with longer wave frequencies? "such as with microwaves". ...
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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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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 ...
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2answers
197 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
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
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 ...
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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
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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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 ...