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

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1answer
10 views

Using Aluminum Cabinet to make Faraday Cage

I am planning on using a solid (solid walls, doors, floor, and top) aluminum cabinet to make a Faraday cage in order to protect electronics against the effects of a possible EMP. I have thought of ...
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2answers
29 views

How to calculate interaction cross section of photons or range of a photon?

Suppose an photon is incidenting on a unit cube metal piece. At the center of the metal piece, the number of electrons is equal to the electron density of the metal per unit volume. What will the ...
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1answer
45 views

Why do gravitational waves or electromagnetic waves exist?

Maxwell equations or Einstein field equations imply the existence of electromagnetic waves and gravitational waves. How can these waves persist on (vacuum) space if they radiate (and loose) energy?
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1answer
17 views

Why are 5G radiations “more easily blocked” even though they occupy higher frequency bands?

The MIT Technology Review article on the advent of 5G communication systems states that: Higher frequencies carry significantly more data. But they are also far more easily blocked by buildings, ...
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3answers
80 views

Is it possible to get steady photon?

When light travels from low density medium to high density medium it's speed decreases according to refractive index of medium. And light is made of moving photons . That means photons are slow downed....
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1answer
44 views

Who will feel force, photon or box?

For Newton's third law to be valid action reaction pair will form . What will they be and why ? In reality , light is emmited when electron jump from high energy to low energy level and after emmision ...
2
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1answer
27 views

Why differential wave equation of EM in dielectrics uses permittivity and permeability of vacuum

If been reading some basic book to understand how to derive the wave equation of light from the Maxwell equations, but those equations use the permittivity and permeability of vacuum, but the books ...
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0answers
18 views

Electromagnetic wave inside a conductor

When considering a coaxial cable it is said that the EM-Wave propagates only in the dielectric between the inner and the outer conductor. But does not also exists a wave inside the inner conductor due ...
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1answer
45 views

How does energy transmission work with antennas?

If we surround an energy emitting radio antenna by large number of energy absorbing radio antennas, do the surrounding antennas have a large effect on the central antenna? The emitting antenna emits ...
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1answer
87 views

Why do I see discrete images when moving an object in front of a screen?

I observed this while doing my homework. I have a habit of shaking my pen between my fingers vigorously while thinking something. My PC's screen is right in front of me (on my study table itself). ...
2
votes
1answer
38 views

How does the interaction of an photon with a free electron in metal and with a isolated free electron differs?

I am curious to know this,its confusing me a lot.How does it differ,What is the interaction cross section for both the cases if an infrared photon incidents on it?.
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0answers
29 views

What effect would constant exposure to 10mw/m2 of rf energy from a DECT baby monitor have on an infant?

Would the radiowaves pass through the body or just cause an imperceptible rise in temperature?
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1answer
30 views

Plane waves in plasmas

Waves in plasmas can be classified as electromagnetic or electrostatic according to whether or not there is an oscillating magnetic field. A corresponding wiki article states: Applying Faraday's ...
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1answer
36 views

Finding number of photons per second crossing an area with distance $d$ from a radiating point

Let's say I have a radio tower with frequency $v[HZ]$ and power output of $P[W]$ radiating uniformly across all directions, and I need to find the number of photons crossing an area of $1m^2$ per $...
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1answer
59 views

Why does the cloud in a straight line as if someone draw a line in the sky with a straight edge?

My cousin took one of these pictures(the middle) in the evening in BKK n she confirmed that she took it with her phone. I've been trying to explain it. I thought it had to do with hot air and the ...
1
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1answer
43 views

Can visible light be composed of invisible electromagnetic frequencies?

I know that when we see red light (via electromagnetic frequencies in the red range) and blue light (via electromagnetic frequencies in the blue range) at the same time, we perceive it as magenta ...
2
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1answer
70 views

Hypothetically, would tapping one's hand, or otherwise vibrating a physical object, at the frequency of visible light produce light? [on hold]

This was inspired by the following just-closed question: What happens if I tap my hand at visible light frequencies? We know that sound can be and is produced by a vibrating object if it is in ...
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2answers
70 views

Contradiction on the behavior of refractive index

The refractive index is given by: $$ n = \sqrt{\mu_r \epsilon_r} $$ This equation is symmetric about wavelength and is same for all wavelength of light i.e. since $\mu_r$ and $\epsilon_r$ are ...
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0answers
83 views

Trying to reproduce curves with angle of CMB anisotropies as a function of distance and curvature parameter

I am looking for a way to get, by a simple numerical computation, the 3 curves on the following figure: For this, I don't know what considering as abcissa (comoving distance ?, i.e $$D_{comoving} = ...
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1answer
39 views

electromagnetic transmission in regards to environment [closed]

I'm interested in the estimation of the distance an electromagnetic signal can be transmitted. Background is that I would like to understand how materials absorb wifi-signals. For example, the most ...
0
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1answer
36 views

Can I change the speed of light in vacuum? [duplicate]

General theory of relativity proved that gravity does attract light ( photons ), what if I project a beam of light radially towards a black holes will it increases it's speed or not?
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0answers
5 views

Passive rfid tag - link between size of antenna and read range ( detailed )? [migrated]

It is often said that as much smaller the tag as shorter the read range .~ Could somebody explain more technically in terms of radio engineering . For instance why the hittachi's u chip cannot ...
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0answers
27 views

Does photon exist? [duplicate]

I believe photon is similar to a mythical creature that serves to be a place-holder interpretation until a better interpretation can replace it. Following are the flaws in photon model, according to ...
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3answers
58 views

Representation of electromagnetic wave? [duplicate]

In Representation of electromagnetic waves we show both electric and magnetic fields perpendicular to each other and having zero magnitude at one point and maximum at other point. This representation ...
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0answers
14 views

Do the moving changes that create an electric field feel a force due to the magnetic field the changing electric field creates?

If you had an AC current running between 2 plates (capacitor), such that an electromagnetic wave was created, would the moving charges be affected by the magnetic field created?
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0answers
30 views

Are all the youtube animations of EM waves wrong? [duplicate]

In the typical youtube animations/drawings of the electric and magnetic field fluctuations, the magnetic field peaks at the same time the electric field peaks. Since a magnetic field is created with a ...
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0answers
17 views

EM mode attenuation paradox - Why one mode disappears?

I designed a photonic structure and in simulation's result I see two reflectance peaks. Those peaks appear, because guided modes arise and the light propagates into the structure, instead of being ...
2
votes
5answers
96 views

Does light’s deflection by a gravitational well vary depending on frequency or other properties of the wave?

I’m curious if the magnitude of the displacement of light by a gravity well is variable to any property of the photons (frequency, polarization, etc).
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0answers
20 views

Radar detections interpretation

I'm not an expert in radar or electromagnetism. I'm having some questions. How do work the radars on the cars. Is the radar giving a point cloud of a object? I know that radar has many reflections ...
3
votes
0answers
41 views

What is the quantum mechanical interaction cross section of a photon during scattering of photons by electrons present in metals?

I don't how to calculate interaction cross section for this process.Can I use Thomson cross section for this process because this process is similar to Thomson scattering,if not ,How to calculate ...
60
votes
4answers
11k views

What's the physics behind XKCD #2027 (time between lightning flash and radio wave burst)?

XKCD usually has solid (and often contemporary) science behind it. Lightning Difference, #2027 one says: Q: What’s that trick for telling how many miles away lightning is? A: Just count the ...
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1answer
42 views

Radio waves collision versus waves in a pond collision

Please see the attached picture: We are trying to show an image to visualize radio wave collision and interference with regards to Maritime AIS Technology. What do colliding radio waves have in ...
1
vote
2answers
39 views

Is there a cap to EM wavelengths

I was just wondering, if there is a cap to the min and max of EM waves. like whats the smallest possible wavelength? the width of an electron? smaller? What kind of wave would that be? And what ...
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1answer
36 views

What are the types of infrared scattering?

There are various types of scattering of electromagnetic wave. what type of scattering involves infrared electromagnetic wave?
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1answer
29 views

Why does the accretion disc radiate energy and matter?

Jets of matter and energy are powered by accretion disc i.e., matter spiralling into the massive black hole at the galactic centre. How is this jet formed? I think that the dust particles and gases ...
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1answer
51 views

Why all EM waves have same speed in vacuum? [duplicate]

As far as I know different electromagnetic waves including light have different frequency and wavelength in Vacuum and other medium as well then which factor makes their speed equal to $c$?
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1answer
54 views

Electromagnetic Wave (Without Magnetic and Electric Field)

As I know, every electromagnetic wave has magnetic and electric field component (perpendicular to the direction of wave). I have a doubt about this, as a hot iron bar also emits EM waves, and as ...
0
votes
2answers
52 views

Will the em wave oscillated by antenna 300MHz AC with 1 V amplitude voltage, have a higher energy, than same antenna config., but with 200 V, and why? [closed]

The DC voltage source provides electrons moves in a single direction, with a single speed( current($I$) shows how much electrons goes through conductor cross-section, hence from the Omh law voltage ...
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2answers
28 views

Separating ultraviolet light waves into UVA, UVB, and UVC

Similar to how a prism may be used to separate visible light into its individual colors, is there any surface or material that will separate ultraviolet light into the three types of UV light: UV-A (...
1
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4answers
80 views

Is it possible to make a vacuum balloon filled with electromagnetic radiation float?

Given the right materials and structure, could you theoretically use radiation pressure to keep a equilibrium amount of pressure inside a special vacuum balloon so that it would float. (ignoring the ...
2
votes
1answer
61 views

How is electro-magnetic wave formed without medium? [duplicate]

There are particles in a medium. When these particles oscillate with SHM motion, a flow is formed. That is called a wave. But when there is no medium, there is no oscillation. That means no flow. ...
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0answers
43 views

How does Einstein's oscillatory & quantum structure of radiation from 1909 relate to modern physics

In his 1909 lecture The Development of Our Views on the Composition and Essence of Radiation Einstein discusses two structures of "radiation": As far as I know, no mathematical theory has been ...
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1answer
32 views

When given light colour and refractive index, how do I find wavelength?

Example situation If I knew that this green light, which has a wavelength of 500 nm in air, travels through a medium with a refractive index of 2.4, how would I find the wavelength in the medium? ...
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1answer
26 views

Wein's Displacement Law for Light Bulbs?

I know Wein's Law $\lambda_{max}=\frac{b}{T}$ works for ideal black bodies. I have some clear glass incandescent light bulbs which have Tungsten as a filament. Would Wein's Law of displacement be a ...
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3answers
38 views

Would it be possible to invert a tokamak to make a solar probe?

I was just browsing random stuff on the internet, and I came across this article about the parker solar probe. The rhetoric was like "oh my, the sun is so hot but the probe won't melt.. etc. etc.", ...
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0answers
24 views

How can we excite transverse magnetic or electric ( TM or TE) modes on metallic mediums?

I would be very thankful if someone can point me at references on explaining theories of excitations for transverse magnetic or electric modes. In engineering, the literature has plenty of papers on ...
0
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1answer
88 views

Why can you make phone calls from inside an airplane?

If you're inside a Faraday cage, you are supposed to be electromagnetically isolated from the outside. But I was able to make a phone call and even use Wi-FI on a plane. Why doesn't this violate the ...
3
votes
2answers
63 views

Is photon something that already exists before measurement?

Do photons actually exist when electromagnetic waves are travelling, or are they thought to exist only because energy always quantizes when it's measured? And if photons really do exist, how their ...
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3answers
72 views

What is the range of electric field of an photon?

Obviously every electric field has an specific range upto which it can have effect on.What is the range from the median line for an electric field of a photon.As most physics textbooks and physicist ...
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1answer
43 views

Cross Product in Spherical Coordinates

I am looking at an example problem from Greiner's Classical Electrodynamics (chapter 21 , page 441) about the Hertzian Dipole where the radiation will require a cross product ($\vec{d} \times \hat{n}$,...