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

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16
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8answers
10k views

Why no longitudinal electromagnetic waves?

According to wikipedia and other sources, there are no longitudinal electromagnetic waves in free space. I'm wondering why not. Consider an oscillating charged particle as a source of EM waves. Say ...
0
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2answers
129 views

What is the least count of the timer clocks used in RADAR?

I was checking out some videos in YouTube regarding the working principle of RADAR. To quote some HOW IT WORKS: World War II Radar (720p), part 1, How does RADAR work? | James May Q&A | Head ...
1
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2answers
47 views

Why is the energy expressed in an electron orbital change of state electromagnetic (photon)? [on hold]

As I understand it, Schrodinger's wave equation predicts the allowable energy states an electron can have under the electromagnetic forces of a given nucleus (and I assume other 'orbital' electrons). ...
3
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1answer
5k views

Optical constants of noble metals: the Drude model for microwave modelling

I have a question regarding the optical constants of noble metals. According to Johnson and Christy's paper Optical Constants of Noble Metals (Phys. Rev. B 6, 4370–4379 (1972), doi:10.1103/PhysRevB.6....
3
votes
1answer
113 views

Is it possible to synthesize an EMW which is not quantized?

( I initially started to ask, "since according to Quantum-theory of light; the energy of a photon, depends only on the frequency of light-wave (E = h * nu), and no-mention of amplitude. So, does the ...
19
votes
2answers
989 views

Could Google scan books without opening them? [on hold]

A few years ago, I read an article about a proposal Google put forward, as part of its paper-to-digital media project, which had the advantage of greatly speeding up the process of scanning text. The ...
16
votes
5answers
899 views

Could cell-phone radiation cause cancer?

It is very crucial that I ask whether it could and not whether it does. I do not mean to be the least controversial. To my surprise, having read "Physics for Future Presidents" by Richard Muller last ...
1
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0answers
23 views

Black Hole Scattering of Low-Frequency Light

What is the far-field interference pattern for low-frequency (i.e., the wavelength is much larger than the Schwarzschild radius) electromagnetic plane wave radiation about a point mass? I envision a ...
-2
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1answer
31 views

Wave nature of light [on hold]

I'm currently working on a project to demonstrate the wave nature of light. Now, my question in specific is: How could the phenomenon of interference be used to MATHEMATICALLY explain the wave nature ...
2
votes
1answer
63 views

How does a photon 'know' when to reflect in case of refraction? [on hold]

In thin-film interference and in glass fibers refraction is involved. Depending on the angle of which a light ray enters the material it will be reflected or transmitted. The refraction depends on the ...
1
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1answer
39 views

What is absorption rate of WiFi and Bluetooth RF in water? [on hold]

Specifically, frequencies 5.75GHz and 2.4-2.485GHz. I want to place a hermetically sealed circuit at the bottom of a gold fish bowl, and want to know if the water will significantly attenuate WiFi or ...
4
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3answers
145 views

Minimum frequency of an electromagnetic wave

Is it possible to create an electromagnetic wave of near zero frequency? An electromagnetic wave carries energy. If we can make the frequency of an EM wave vanishingly small and make it practicality ...
14
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5answers
2k views

How many photons are needed to make a light wave?

What is the smallest number of photons needed to make a "light wave"? In other words, how many (coherent?) photons start to exhibit classical behavior? For example, how many photons are needed to get ...
14
votes
3answers
1k views

The speed of light upon reflection [duplicate]

(NOTE: I am an 8th grader, so I may not be capable of perfectly elaborating my point by scientific measures. Also, English is not my first language) I have read that the speed of light is constant, ...
4
votes
2answers
355 views

Principle of Reflection on atomic level

The well observed phenomenon has besides several others has always been a fascination to me, we are well aware of several theories, experiments and practical applications of the well known phenomenon. ...
8
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5answers
4k views

Explain reflection laws at the atomic level

The "equal angles" law of refection on a flat mirror is a macroscopic phenomenon. To put it in anthropomorphic terms, how do individual photons know the orientation of the mirror so as to bounce off ...
3
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0answers
52 views

How to correctly calculate the colour of the sky?

It is well-known that the sky is blue due to Rayleigh-scattering. What bothers me though is the question how to actually calculate the spectrum of the scattered sunlight. Yes, use one of the ...
11
votes
2answers
3k views

Why is light described by a null geodesic?

I'm trying to wrap my head around how geodesics describe trajectories at the moment. I get that for events to be causally connected, they must be connected by a timelike curve, so free objects must ...
3
votes
2answers
109 views

How is light related to photons? [duplicate]

This may seem like a duplicate but I do not understand other explanations. I have read that light is an electromagnetic wave (a fluctuation or disturbance in the electric and magnetic field). How ...
19
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6answers
2k views

Why does matter/antimatter only produce gamma rays?

According to wikipedia, all antimatter annihilation produces gamma rays (along with potentially other elements). Why specifically Gamma rays? Why not electromagnetic waves of other wavelength?
0
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0answers
16 views

Tesla's radiant energy system [closed]

Would Tesla's radiant energy system work better on earth if there was no magnetosphere, and more radiant energy from the sun is able to reach the system? Thanks!
-1
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0answers
38 views

A rocket is receding from the earth at [closed]

A rocket is receding from the Earth at speed of $0.2 c$ where $c$ is velocity of light. It emits signals of frequency $4 \times 10^7 $Hz. The apparent frequency observed by an observer on earth is
-1
votes
0answers
19 views

What is the relation between geometric dilution and optical depth? [closed]

Is there any relation between geometric dilution and optical depth? Please help! PS: if we consider a star of radius R, its observed intensity at a distance 'r' is given by I= WI*, where 'I*' is the ...
1
vote
1answer
41 views

What is the quantum (e.g. Photon) phenomena that represents the EM wave impedance?

The EM wave impedance of free space is said to be ~377 ohms and represents the ratio of Electric field strength (E) to magnetic field strength (H). So that: $$ \frac{E}{H} = ~377 \,\Omega $$ When ...
-1
votes
1answer
46 views

Change in Speed of Light [duplicate]

Whenever light enters from air to glass its speed decreases but when it cross the glass and again come in air its speed increases. What is the reason behind this property? What is slowing it and what ...
0
votes
2answers
28 views

Gamma spectroscopy - Nuclide identification

I have a question about what the usual practice is for nuclide identification in gamma spectroscopy. For example, if I see a line at 477 keV, I would write that the origin of this line is $^7Be$. As ...
16
votes
4answers
2k views

To what extent can speed of light be reduced? [duplicate]

Light slows down upon entering different transparent objects, and the ratio is taken as refractive index of the object. If light can be slowed down, then is there a limit up to which it can be slowed ...
1
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1answer
39 views

Is the electromagnetic wave produced by a linearly accelerating charge sinusoidal?

I have just learnt that accelerating charges produce electromagnetic radiation. When a charge initially at rest suddenly accelerates, the transition between the new and old elctric field lines ...
0
votes
1answer
55 views

Cardboard allows AM/FM waves but NOT light - Why?

I am going through Electromagnetic waves. In footnote, the author was giving illustration on transparency of materials. Was going through some references here as well as in Google. Many people ...
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votes
2answers
70 views

Properties of electromagnetic radiations with respect to wavelength [closed]

If two electromagnetic waves have same wavelength, does that implies both of them have same frequency and intensity?
13
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3answers
1k views

Can the speed of light become complex inside a metamaterial?

The speed of light in a material is defined as $c = \frac{1}{\sqrt{\epsilon \mu}}$. There are metamaterials with negative permittivity $\epsilon < 0$ and permeability $\mu < 0$ at the same time. ...
0
votes
0answers
71 views

In a moving light clock, does the velocity of the clock add to the velocity of the light?

Currently going through the class Space, Time and Einstein from worldscienceu. On module Time in Motion an example is given of 2 light clocks, one moving and one stationary. The point is made that ...
0
votes
1answer
27 views

Why do Very high frequency (VHF) radio waves have limited range?

Why do ultra high frequency radio waves (ex: 2.4GHz or 5GHz) have limited range ?Is it to do with absorption ?If so how do these waves get absorbed when the ELF waves are not ,and on the other side ...
0
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2answers
362 views

Absorbance by using Poynting vector

How should I compute the amount of energy of an EM wave absorbed by a material? Can I just use the divergence of the Poynting vector?
3
votes
1answer
25 views

Transmission line model proof?

Why 2 distributed lines is represented with series inductor and resistor along with parallel capacitor and resistor? What is the motivation for that? In circuit theory I Knew the assumptions to ...
2
votes
1answer
14 views

Intensity of EMR and time dependence

I imagine an electromagnetic wave as the propagation of electric and magnetic fields. Consequently the amplitude of the field vectors are time-dependent. I also know that the intensity is ...
2
votes
2answers
36 views

Can an electromagnetic wave be split into multiple longer wavelength waves?

Is there any way to convert short wavelength (visible light/near infrared) electromagnetic waves into multiple long wavelength waves (microwave) of near equal total energy? Heating a blackbody with ...
4
votes
1answer
279 views

Why do planets not radiate EM waves in their orbits?

Despite being overall near-netural, I would expect the individual electrons and proton to radiate long EM waves as we accelerate around the Sun or rotate around our poles. Is the acceleration so small ...
2
votes
2answers
68 views

Why do smartphones need towers to send messages? [closed]

Why do smartphones need towers to send messages? Why can't they send messages directly to each other?
0
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0answers
25 views

Why is the phase change of a reflected light ray one quarter wavelength?

Suppose a photon beam impinges on a half-silvered plate such that half of the photons are reflected and other half are transmitted. If $\lvert A\rangle$ is the state vector of the incident ray, and $\...
0
votes
1answer
13 views

How would I construct an EMI shield for low frequency EMI?

By low frequency, I mean 30-100 Hz. Would a Faraday cage or something like it be feasible? I am trying to shield two separate locations on a high voltage cable.
0
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1answer
27 views

Can antennas work with high frequency EM waves?

Antennas usually work with FM waves, and AM waves, which mostly used in telecommunications. Information is transferred on FM, and AM waves by a transmitter transmitting information on these EM waves. ...
1
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1answer
39 views

Is it possible to create a Faraday cage transparent to only violet/blue light from natural white light?

If a Faraday cage’s hole size determines the wavelength of light which can penetrate it then I would imagine this would be possible.
7
votes
4answers
302 views

How do electromagnetic waves carry energy?

Its said that electromagnetic waves carry energy. Is this because these waves are made up of electric and magnetic fields which can cause changes to the stuff that falls with in their range? Is that ...
9
votes
1answer
156 views

Optical chirality and its possible hierarchy of generalizations

Optical chirality refers to a constant of motion of the electromagnetic field, which measures in some sense how chiral a light field is. Specifically, the pseudoscalar quantity $$ C=\frac{\...
0
votes
1answer
33 views

Can photons excert radiation pressure after negative interference? [closed]

Motivation: understanding the EMDrive In the context of speculating how the EMDrive radio frequency resonant cavity thruster may work, in case it turns out to do that, there is one point that really ...
0
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1answer
108 views

Amplitude of eliptically polarised light

In elliptically polarized light, can one define something called amplitude of Electric field? If yes, how do we determine it?
2
votes
4answers
122 views

How can fields interaction give rise to particles?

We say light a matter-wave, meaning along with its wave property it shows particle nature. But how can fields interaction (electric and magnetic) give rise to particles (photon)? I wish someone could ...
1
vote
3answers
66 views

Why conductors don't scatter light?

Air molecules can be oscillated by E field and re-radiate EM waves in different directions. However, if light is shined to a conductor the E field oscillate the free charges but the effect is to ...
4
votes
2answers
136 views

How many photons are there in free space on average

Estimates of the amount of for example "dark matter" are of interest to the cosmologists. However, I have never seen an estimate of how many "free" photons could be speeding about in the known ...