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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5answers
17k views

Phase shift of 180 degrees on reflection from optically denser medium

Can anyone please provide an intuitive explanation of why phase shift of 180 degrees occurs in the Electric Field of a EM wave,when reflected from an optically denser medium? I tried searching for it ...
1
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0answers
41 views

The interaction between waves and particles according to their wavelength [duplicate]

Why do EM waves with a large wavelength like those in the red range (and radio waves) interact with particles less than those in the blue range? That is the reason why the sky is blue, is that right? ...
1
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1answer
32 views

In a noiseless environment, how accurate do today's transmitters send EM waves?

Suppose that there is no external noise in the environment. How accurate are today's TEM wave transmitters in such a case? So if we want to send $200\cos(1000\pi t)$, can transmitters send exactly ...
1
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2answers
108 views

Does a source emitting visible light also emit infrared, microwave and radio waves?

I have a bulb which is hot enough to emit visible light and obviously it's hot enough to emit radiation which lies before the visible light temperature i.e. radio waves, microwaves, and infrared ...
0
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1answer
103 views

Find the electric field of light due to an LED [closed]

This is a JEE mains question which neither me, nor any of my teachers can figure out. Help me here. "A red LED emits light at 0.1 watt uniformly around it. The amplitude of the electric field of the ...
1
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2answers
98 views

Why does the light instantly disappear when we switch off the source?

For example i take a box which is completely covered by the most perfect mirrors possible inside and inside that box i have a bulb whose bulb holder is also covered with the most perfect mirrors ...
0
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0answers
42 views

What have we built? A resonant loop antenna? Rhombic?

Some background, my partner and I have built an antenna we are supposed to characterize for an assignment, and compare it to physical predictions. However, we don't know what type of antenna we have ...
0
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2answers
1k views

Does travelling light help us see past versions of an object?

I saw a passage in my son's homework book, constructing a scenario in which a person standing on a planet 65 million light years away from Earth, with an extremely powerful telescope pointed at Earth, ...
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2answers
210 views

How does Huygens Principle explain interference?

How exactly does Huygens theory about the propagation of wavefronts account for interference?
7
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2answers
357 views

Measurement of blueshift from Andromeda galaxy

How the blueshift from Andromeda galaxy was measured? Since the measurement of blueshift/redshift has to do with the identification of relative distance of spectral lines how this identification is ...
1
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4answers
203 views

Non-complex proof that the electric and magnetic fields are perpendicular in a plane wave

I'm looking for a proof that the electric and magnetic fields in a plane wave are perpendicular that doesn't invoke complex E and B fields. I haven't been able to find one. If the proof requires ...
6
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3answers
917 views

Why is it hard to detect a black hole

I've read in some texts that we can't directly observe a black hole in space because not even light can escape from its gravity. Some of the indirect observational methods mentioned are, gravitational ...
5
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2answers
884 views

Why do we use microwaves in microwave oven?

We know that any object above absolute zero emits electromagnetic radiation. So hotter the object shorter the wavelengths. In the electromagnetic radiation spectrum radio waves has the longest then ...
0
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3answers
117 views

What is the direction of the magnetic vector potential in an electromagnetic plane wave?

The vector potential $A$ is perpendicular to $B = \nabla \times A$, by definition, and hence, in a plane wave, it is either in the direction of $E$ or the direction of propagation. I suspect it is in ...
45
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3answers
7k views

Why doesn't light affect a compass?

In our daily life a lot of photons of visible light, infrared and radio etc move around us. We know that light is an electromagnetic radiation. So why doesn't that electromagnetic radiation affect a ...
1
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3answers
138 views

Why can't light escape a blackhole? [duplicate]

Gravity attracts objects which have mass right. We know that light is massless so why does a black hole's gravity attract light?
3
votes
3answers
301 views

How much of the universes mass is bound up in photons traveling between stars?

I was watching a Scott Manley video on youtube and he mentioned that the Sun was loosing 4 million tons of mass a second as it converts to energy. With a few trillion trillion stars also converting ...
0
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2answers
103 views

How does light oscillate?

Why do we say that electromagnetic wave is oscillating? Or does light propagate really in a wavy form like this image? What is making the photons oscillate and how is it oscillating is it ...
0
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1answer
31 views

Difference between a light wave in space and a wave in a pond

Apart from their nature and the medium utilized, what are the differences between an EM wave and a wave we see in a pond? When we throw a stone into a pond, can we imagine we are observing light ...
9
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1answer
2k views

Why is black the best emitter?

Why are emitters colored black better emitters than other colors? Why is white a worse emitter?
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2answers
205 views

If gravitational waves exist are they technically just another form of light/electromagnetic wave?

I would imagine a gravitational wave would have very similar characteristics to electromagnetic wave, what kind of differences are there?
0
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1answer
76 views
15
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3answers
1k views

Why is the bottom part of a candle flame blue?

What’s the explanation behind the bottom part of a candle flame being blue? I googled hard in vain. I read this. I don’t understand how it’s explained by the emission of excited molecular radicals in ...
0
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0answers
29 views

Power radiated by a rotating annulus

I'm trying to solve a homework-kind of problem and I don't expect anyone to give me the solution. Rather, a little push in the right direction and tell me whether I made some mistake(s). Consider a ...
2
votes
1answer
72 views

Can a nuclear bomb be used as the power source for a laser beam

My previous post "Using nuclear bombs to detect near earth orbit objects" asked about using nuclear devices to detect Earth directed asteroids and low albedo comets. Now I want to explore a method of ...
2
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3answers
110 views

How does an Inductor “store” energy?

It seems to me that an electromagnetic field is nothing more than a collection of photons, which as I've heard, extends through space infinitely. Why is it, then, that an inductor such as simple ...
0
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1answer
44 views

Building a Crystal Radio Questions

I have been reading several books and articles about building a crystal radio and the explanations about the inner workings of the circuit seem vague. All articles and books mention the coil and the ...
1
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2answers
89 views

Models of light

As far as I'm aware, there are two different (and almost contradictory) models that describe the behavior of light: light as a wave (EM), and light as a particle (QM). From what I've heard, depending ...
5
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4answers
848 views

Gravitational lensing or cloud refraction?

My current understanding of gravitational lensing follows When a star or other massive body passes between us and another star, the phenomenon generally labeled 'gravitational lensing' occurs. The ...
0
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3answers
88 views

How does an electromagnetic field oscillate if time does not pass for the speed of light?

As far as I'm aware, traveling at $c$ will prevent time passing due to time dilation. Electromagnetic waves rely upon oscillations to propagate. Since oscillations rely upon the passing of time, how ...
4
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3answers
201 views

Why most of physics is somehow related to light? [closed]

It seems that for the past 200 years, every physicist is concerned about light. For example : Newton's particle model, Young experiment, Photo-Electrict effect and Einstein's formula, Special ...
0
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2answers
134 views

Why is the spectrum of a blue flame the way it is?

In the spectrum of the blue part in a candle flame, there’s a violet emission at 432 nm due to excited CH* molecules (chemiluminescence). Why 432? Why not 400 or 500? There are emissions at 436, 475 ...
0
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1answer
27 views

Monochromatic wave between two conducting planes

I'm trying to do a question which reads: Perfectly conducting planes are positioned at $y=0$ and $y=a$. Show that a monochromatic wave may propagate between the plates in the direction $z$ if the ...
6
votes
1answer
819 views

Test whether a glass prevents you from getting your Vitamin D portion?

I work in an office with glass, which I believe filters the UV radiation of the sunlight. Is it possible to test if exposure to the light coming through the glass will supply Vitamin D for me as a ...
0
votes
2answers
189 views

Do electromagnetic waves occupy varying amounts of space, or do they simply vary in magnitude?

The above diagram shows an electromagnetic wave propogating in the $x$ direction, if the electric field is in the $y$ direction and the magnetic in the $z$ direction. I was taught however that the ...
-2
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1answer
398 views

Is Magnetic Field is made of Photon? Is there any frequency of Magnetic Field waves? [duplicate]

(Considering the What is a magnetic field question which is asked on just 8th march, by @DragonSlayer3 and my own question which is left with negative points and closed, Photon Energies in sunlight, ...
2
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0answers
73 views

Higher order multipolar second harmonic generation in centrosymmetric materials

As is pointed in this question, second harmonic generation is forbidden in the bulk of the materials possessing centrosymmetry. In some papers it is said that in the dipolar approximation the SHG ...
3
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2answers
129 views

Do photons with a frequency of less than 1 Hz exist?

A photon with a frequency of less than 1 Hz would have an energy below $$ E = h*v < 6.626×10^{−34} J $$ which would be less than the value of Planck's constant. Do photons with such a low energy ...
6
votes
3answers
880 views

Why does the electric field dominate in light?

I read a book on the wave property of light where the author mentioned that the electric field, instead of magnetic field, dominates the light property. I don't understand why. In Maxwell's theory, a ...
30
votes
13answers
47k views

Why is light called an 'electromagnetic wave' if it's neither electric nor magnetic?

How can light be called electromagnetic if it doesn't appear to be electric nor magnetic? If I go out to the sunlight, magnets aren't affected (or don't seem to be). And there is no transfer of ...
1
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2answers
192 views

EM wave in Real life

everyone I'm new here, but not so new in physics. I have read many articles about EM wave to find what I'm searching for and nothing still. I have seen many pictures, animations and videos about EM ...
0
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1answer
66 views

I am missing some relation between ampitude and intensity

Suppose a lamp emits monochromatic light uniformily in all directions. Let the lamp be 3% efficient in converting electrical power to EMW, and consumes 100W of power. At distance of 5m, in an area of ...
0
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0answers
20 views

Is energy discrete [duplicate]

It is often stated that because the energy in an em wave is $E=hf$, the energy comes only as multiples of $h$, ie quantized. But we know that $f$ is a real number, and you could have fractions of one ...
2
votes
3answers
143 views

Is it possible to create a beam of light with frequency of 0?

Is it possible to create a beam of light with frequency of 0? So this would involve photon(s) that move forward without fluctuating with any frequency. If yes, how could this be done? Also, ...
1
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1answer
29 views

Does the wave/particle duality exist across the entire electromagnetic spectrum? [closed]

Does the wave/particle duality exist across the entire electromagnetic spectrum? If theory says so, then to what extent have physicists confirmed by experimental means?
6
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6answers
11k views

How many colors exist?

How many "colors" do exist? Our perception: As far as I know, colors are just different frequencies of light. According to wikipedia, we can see wavelengths from about 380 nm und 740 nm. This means ...
29
votes
4answers
4k views

Is there an infinite amount of wavelengths of light? Is the EM spectrum continuous?

The electromagnetic spectrum is a continuum of wavelengths of light, and we have labels for some ranges of these and numerical measurements for many. Question: Is the EM spectrum continuous such that ...
2
votes
0answers
79 views

Phased non linear array antenna - First Sidelobe

I have a problem I cannot seem to solve and I REALLY need some help. It's about phased-array antennas whose dipoles are not equally spaced, not equally phased, not equally fed (amplitude). Let's ...
3
votes
2answers
141 views

Do light particle/waves have a frequency? [duplicate]

I sought the answer to the question about amplitude of light waves first, but I was actually thinking about whether the wavelength is the only property of a single quanta of light. I suppose direction ...
1
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2answers
230 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- ...