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

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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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2answers
50 views

What is the difference between xrays and ultra violet rays?

Do they differ in just frequency and wavelenght ? Or there is more about it
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2answers
101 views

Radiation emission and absorption

Any object can emit and absorb radiation and the power of emission can be represented by the Stefan-Boltzmann law: $$P=A\epsilon\sigma T^4$$ In many texts the net power radiated is the difference ...
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25 views

Could an object higher than the stationary orbit be returned to the outgoing point on this orbit?

In the question Centrifuge speed of an object higher than a stationary orbit, I asked: Does an object higher than the stationary orbit move slower or faster around the world than the top of a tower ...
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1answer
21 views

A confusion on Radiations emitted from a body [duplicate]

Suppose an atom is accelerated...Now the protons in its nucleus and the electrons in the orbits are also accelerated...So will they emit the electromagnetic radiations? Basically here the electrons ...
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1answer
22 views

How can we derive that an accelerated charge particle will radiate EMWs?

All the properties of the electromagnetic entity is said to be fully described by the four golden rules of Electromagnetism : The Maxwell's Equations.How can we derive that a charged particle will ...
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31 views

Experimentally diminishing random errors for low wavelength UV observations

Part of the work that I do involves observations of solar low wavelength UV observations, specifically UV-B and UV-A II (up to 340nm). I have noticed that when I observe responses on a CCD or CMOS ...
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1answer
67 views

Could airport security devices detect differences between printed and written documents?

If airport security scanners of any kind (xray, thermal, whatever else they use) looked at two items: A printed paper textbook The same printed paper textbook into which we have inserted a regular ...
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1answer
49 views

About accelerating particles [duplicate]

Can a particle moving below the speed of light be accelerated more and more until it is travelling at say c/2? IF so does it behave like electro-magnetic radiation?
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0answers
26 views

Is a smartphone with a radar possible? [on hold]

Is any form of radar possible with the sensors in an iPhone 5s ? Could you use the speaker and microphone to do sonar?
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1answer
45 views

Absorption of waves in a plasma

Suppose a plasma has characteristic frequency $\omega_p$. Since $$n = \sqrt{\left(1-\frac{\omega_p^2}{\omega^2}\right)} $$ For $\omega<\omega_p$, the refractive index will be imaginary - which ...
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1answer
87 views

Blackbody and standing waves

I'm reading articles about black body radiation and why classical mechanics fails to explain it. My question is: Why do EM waves have to be standing wave in a cavity?
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1answer
21 views

When is the displacement current equal to conduction current in case of a parallel plate capacitor being charged?

I came across a text - "Whenever a conduction current is oscillating in time, the displacement current is equal to the conduction current in case of parallel plate capacitor." I am not sure what's ...
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0answers
31 views

What is the highest frequency directly detected?

The Feynman Lectures of Physics states: In fact, although we mentioned many frequencies, no phenomenon directly involving a frequency has yet been detected above approximately $10^{12}$ cycles per ...
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0answers
32 views

Rotating sheet of light

I am looking for references on "rotating sheets of light" generated from a point source. Mainly I am looking for applications. (I saw a use related to climate studies or weather forecasting, where a ...
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4answers
725 views

Can light waves cause beats?

My question is pretty brief. When two sound waves of nearly same frequencies interfere, we get beats. But, I have not observed something like that happening in the case of light. In fact, most of the ...
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1answer
76 views

Electromagnetic waves in an antenna

There is a few questions that need to be answered in detail but in an easy way... What does it mean to describe the 'plane of polarisation' of electromagnetic waves? Why will some antenna have rods ...
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1answer
64 views

Angular momentum of light

Can someone explain the classical angular momentum in electromagnetic theory of light? If I shine elliptically polarised em wave on a black disc it rotates. I would like to know how to calculate ...
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3answers
80 views

Why does gravitational lensing bend light rather than absorbing it?

I've read that gravitational lensing bends the light; I am a little confused about black holes and why lensing produces different results. Black holes absorb light whereas lensing should have also ...
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1answer
482 views

Dark matter a medium for light propagation

Is dark matter a candidate to fill void left by luminiferous ether as a medium for light travel?
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3answers
36 views

Difference between high-level and low-levels of electromagnetic radiation

can someone please explain me what we mean by 'high-level' or 'low-level' in electromagnetic radiation? for example, it is believed that high-level microwave radiation is harmful to human but not the ...
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1answer
32 views

Wave frequencies and barrier width?

I know a fact that says a wave can go through barriers thinner than its length. This is why for example FM radio can be picked anywhere while antenna TV needs direct sight to the transmitter. Is this ...
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5answers
713 views

How is a vacuum able to propagate light?

We say that sound waves need a medium to propagate and we know that light doesn't need such a thing. But is that really how that works? There's no such thing as "nothing" according to Quantum ...
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1answer
139 views

Can we draw analogy between em power flow through free space and ac power flow through a transmission line?

Knowing that the free space has a characteristic impedance (which is purely resistive, measured in ohms) I was wondering if I can model the free space as an infinitely long transmission line- ...
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3answers
3k views

Real and imaginary parts of dielectric constant vs refractive index?

So for a complex dielectric constant $\epsilon = \epsilon_a + i\epsilon_b$, the wave vector and index of refraction are related to it through $k = \frac{\omega}{c}n$ and $n = \sqrt{\frac{\mu ...
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1answer
135 views

What is absorption of an electromagnetic wave?

Can any one explain the absorption/transmission/reflection of electromagnetic waves in the wave form? It is generally said that the atom absorbs/reflects/transmits photon. But can this phenomena be ...
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0answers
66 views

How is Energy Distributed within a Electromagnetic Wave?

Let $$\hat{H}$$ Denote the full energy of the electromagnetic wave. Now is it right to assume that $$\hat{H}=\sqrt{2\hat{H}_y^2+\hat{H}_x^2}=\sqrt{2\hat{H}_z^2+\hat{H}_x^2}$$ If not, what is ...
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3answers
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Is there any example where electric and magnetic fields are not perpendicular?

Perpendicular electric and magnetic field creates light or other electromagnetic waves. Is it a necessary property to have a perpendicular fields? If not what would happen when the fields are not ...
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1answer
92 views

Admixtures of longitudinal and timelike photons!

In the quantization of electromagnetic field the physical states $|\psi\rangle$ are found to obey the following relation: $[a^{(0)}(k)-a^{(3)}(k)]|\psi\rangle=0$ It is explained as the physical ...
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2answers
74 views

Can someone explain to me the concept of atmosphere opacity?

On this diagram, why is the atmospheric opacity shaped as it is? If we are able to see lights due to low atmospheric opacity, why can't we see radio waves, when the atmospheric opacity is so low ...
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1answer
104 views

Probability density of detection of collinearly emitted photons in two detectors

Update: As proposed by @dmckee, I added equation numbers and improved the display of some equations. The answer by @Trimok inspired me to look at coordinate systems which are not specific to the ...
2
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1answer
56 views

Earnshaw Theorem for ionic solids

Is a single molecule of sodium chloride (say) or a cluster of molecules of NaCl unstable, although macroscopically NaCl is in fact, stable? How can I reason this based on Earnshaw's theorem?
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1answer
48 views

Electric charge of light? [duplicate]

Light (or any radiation as a matter of fact) is an electromagnetic wave so why doesn't it have a electric charge associated with it? As far as I know only static or flowing electric chargers can ...
2
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2answers
286 views

Which cyan colored line is produced in the Thomson e/m apparatus?

Related: Which green spectral line(s) are emitted in a Thomson tube? After reading Lisa Lee’s OP on an electron deflection tube, although she had some misunderstandings on its operation, I still ...
2
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1answer
46 views

Import of Celestial Effects on Satellite Radio Interference

Some internet (among other) infrastructure comprises satellites, which beam communications in radio frequencies. These satellites, to ground observers, appear as very small solid angles in the sky. ...
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1answer
69 views

What does the size of an object have to do with it's color?

Stephen Hawking mentions in his book 'A Brief History of Time' that quarks are much smaller than the wavelength of visible light so they do not have any color in the normal sense. What exactly does ...
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1answer
63 views

Is the photon first a wave, then a particle? [duplicate]

When the 'photon' is emitted, it would reason that the result of the energy fluctuation that creates 'it' rather is created as an energy wave, which when measured by us or a surface, it 'becomes' as a ...
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2answers
42 views

Internal energy and photon absorption

I just wish to confirm whether my understanding is correct. I know that photon absorption/emission brings about quantised changes in electron energy levels. Photons (infrared) also interact with ...
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2answers
51 views

How hot particles can get [duplicate]

One way in which an object is affected by temperature rise is that the wavelength of the radiation it emits is gets smaller and smaller. Another way of looking at it is that as an object gets hotter, ...
2
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1answer
70 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 ...
2
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2answers
74 views

Blackbody radiation through quantum mechanics perspective

While explaining black body radiation, the body is assumed as a cavity radiator and the radiations are due to the oscillating electrons. But we know that the electromagnetic radiation emitted is ...
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2answers
467 views

Is data which rides on the carrier frequency dangerous?

My understanding of broadcasting data via electromagnetic radition is, that the data "rides" on a carrier frequency on which it is radiated. I am aware of the fact, that those carrier frequencies are ...
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1answer
35 views

Can we multiply an electromagnetic field?

can we multiply light by a sequence of reflections in a closed vessel? also, is light a part of EM wave? can we multiply the radio wave or EM wave from a transformer?
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2answers
35 views

Parallel electric and magnetic field in traveling wave

Can we have elctromagnetic waves which are characterized by parallel electric and magnetic field $\vec{E} || \vec{B}$ ? I am not talking here about free space, but maybe some kind of materials or ...
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0answers
15 views

Can various wavelengths participate in C/D Interference?

My question is can multiple wavelengths or at least two different wavelengths interfere with one another? I know that they usually have to be the 'same' wavelength, but you'd think they can vary a bit ...
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1answer
52 views

If sound travels through matter what medium does light travel through? [duplicate]

So sound is a wave and is basically just vibrations, an atom vibrates causing another next to it vibrate and so on until it finally reaches our ears to become sound. If that's normally how waves ...
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2answers
104 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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2answers
57 views

Why group velocity represents energy or information transmission? What relation between phase velocity and special relativity

I have two question, why group velocity represents energy or information transmission? what is the relation between phase velocity and Special relativity: why can it exceed C without violation of ...
34
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5answers
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 ...
42
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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 ...