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

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What is energy of light, as we know speed of light?

1.What is total energy of EM waves, as all got same speed? If two em waves has same energy, do they have same mass? If same mass and energy, do they have same frequency or wavelength still ...
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1answer
51 views

Single photon pulse and its electromagnet field

I describe the temporal distribution of a single photon pulse in an interferometer experiment in vacuum via the Gaussian function $\psi$: $$ \psi(t) = \tfrac{1}{(2\pi\sigma^2)^{1/4}} \text ...
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16 views

What is the effect of alpha particle on a diamagnetic substance?

Can alpha particles induce static charge on diamagnetic substances or temporarily magnetize when they are bombarded on them ? If yes then for how much of time the charge remains on it ? Till what ...
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4answers
719 views

Why is an opaque body opaque?

When does a body qualify to be called an opaque body? Is it anybody which cannot let visible light through it or is there any other definition? And when and how does a body allow radiations through ...
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46 views

How to represent a laser pulse in quantum optics

Every quantum optics textbook that I've found says something like "a coherent state represents the output of a laser", but a coherent state is a static thing (aside from the oscillating phase of the ...
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1answer
35 views

Tranverse electromagnetic waves

TEM waves do not exist in waveguide. Is this the correct explanation- Both curl and divergence of TEM are zero inside the waveguide and because of the boundary conditions (electric field zero at every ...
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1answer
23 views

Chaff-RF Relationship?

What is the relationship between chaff length and the frequency it is meant to interfere with? I've read that specific lengths of chaff are more effective as a countermeasure for specific ...
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3answers
439 views

If I turn the light off in a room why does the light instantly disappear? [duplicate]

So today I was asked a question which I found very simple yet I honestly couldn't explain (embarrassingly). One of my mum's friends who knows I'm a scientist asked me "If I turn the light off in a ...
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2answers
175 views

How exactly does applying the Equipartition Theorem to radiation leads to UV catastrophe?

I'm reading a book by George Gamow, "Thirty years that shook Physics" and have trouble understanding his way of describing the UV catastrophe. In a first part he points out that applying the ...
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2answers
283 views

2.4Ghz microwaves have a 12cm wavelength. How do microwave ovens leak radiation, since any gap in the shielding is much smaller than that wavelength?

I've read (I think on wikipedia, but I can't find the reference) that microwave oven leakage is often due to faulty seals on the door. Given that any gap in the door is going to be far smaller than ...
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1answer
99 views

How does the electric field pulse propagate during a change in the magnetic vector potential?

The electric field in terms of the electric scalar potential, and the magnetic vector potential is: $E = -\nabla\phi - \frac{\partial A}{\partial t}$, where $A$ is such that $B = \nabla \times A$. ...
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1answer
106 views

How does Huygens Principle explain interference?

How exactly does Huygens theory about the propagation of wavefronts account for interference?
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43 views

Understanding the definition of SAR value?

I am confused over the meaning of SAR values and different standards in its definitions. While checking of website a mobile manufacturer company for a mobile phone, I found this statement The SAR ...
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1answer
52 views

Tesla Coils - Is there a risk that the discharge can create x-rays?

I've built a Tesla coil that stands about 3 ft tall and uses a spark gap as the interrupter for the primary circuit. Judging by the size of the streamers it's reaching at least a million volts. ...
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0answers
27 views

What would happen to the Earth's atmosphere if all the solar radiation was in the extreme ultraviolet?

According to this, our Earth's atmosphere is completely opaque to radiation with wavelengths less than 100 nm as this radiation has enough energy to ionize the air. Since the surface temperature of ...
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3answers
76 views

Negative frequency contributions for very short pulses?

I am wondering if very short optical light pulses can have a Gaussian envelope? When I describe the pulse shape with a Gaussian than the frequency distribution has also a Gaussian shape. But if the ...
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1answer
243 views

What causes the light spectrum to appear on oil surface? [duplicate]

I have observed that when petrol or oil leaks, the light spectrum appear on it. What causes light to split into its constituent colours?
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3answers
194 views

How is a photon measured?

If photons transmit the electromagnetic force, which is observable: the photon or the electron? Do we ever directly measure a photon, or do we only measure it's effect on electrons. For example ...
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6answers
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Is a suit that hides a soldier's heat signature fundamentally possible?

I recently played "Crysis", a game where the protagonist wears a suit that allows the player to hide both himself and his heat signature. Then I watched Iron Man 3, where a kid suggests that Tony ...
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0answers
14 views

Main differences between elastodynamic and light scattering when using S-matrix to find bound states

What are the main differences (top 5 if question is too broad), for using the S-matrix to find bound states, between elastodynamic and light scattering? (if it facilitates a higher quality ...
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1answer
57 views

What are the advantages of Magnetocardiography?

I am reading the book Bioelectromagnetism by Malmivuo: Difference between the bioelectric and biomagnetic measurements lies in the sensitivity distributions of these methods. Diverse technical ...
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1answer
70 views

Reflection of two electromagnetic waves

Can Electromagnetic waves be reflected by another electromagnetic wave without having any physical (transparent or opaque) material (i.e., in free space with one wave having twice the amplitude of the ...
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0answers
25 views

Near field and Nuclear magnetic resonance (NMR)

Why does Nuclear Magnetic Resonance (NMR) physics not concern itself with near field physics? All resonance wavelengths in NMR are much larger than bough sample, pick-up coil and excitation coil. ...
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2answers
307 views

Linear vs. quadratic dispersion relation

In wave mechanics the dispersion relation between frequency $\omega$ and wave number $k$ is linear: $$\omega_n=c k_n$$ But in quantum mechanics, based on Schrödinger's equation, one can show that we ...
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203 views

Why can't de Broglie waves be electromagnetic in nature?

We know that the wavelength of de Broglie waves for a photon is same as that of the wavelength of the electromagnetic radiation that carries this photon. Doesn't this prove that matter waves are em ...
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2answers
154 views

How the polarization of electromagnetic wave is determined?

What help us determine the polarization of electromagnetic wave . Does perpendicular electric and magnetic field determine it or does the direction of propagation ?
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67 views

Question on electromagnetic wave propagation [closed]

how to do part d of this question? i have done part 1 to three but part d is bit confusing.
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722 views

Is there a difference between the speed of light and that of a photon?

As in the title I am curious whether there is a difference between the speed of photon and the speed of light, and if there is what is the cause of such a difference?
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31 views

EM Fields Transmitted from an antenna and photons [duplicate]

What is the relationship between The EM waves (light) and photons in some context i studied light as photons and others as EM fields but how they are related....another questions : what's the name of ...
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39 views

Analogy for Rayleigh scattering

This morning's eclipse has me looking into Rayleigh scattering. I'm trying to think of a good analogy to explain it to somebody without getting too in-depth into electromagnetism and other subjects... ...
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0answers
65 views

Clarification about Bragg's law explanation

The Wikipedia has this illustration of Bragg's law and then says The two separate waves will arrive at a point with the same phase, and hence undergo constructive interference, if and only if ...
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3answers
53 views

Why radiant heat only travels as infra-red waves and not as other types of em waves like UV rays

Heat is a form of energy and em waves carry energy as momentum of photons. So, I think, radiant heat can travel at any frequency. Please correct me.
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2answers
837 views

Why are EM waves transverse?

I was reading Griffiths' Introduction to Electrodynamics, specifically the section on plane waves. I can see that if we want a transverse wave traveling in the $z$ direction that we are only going to ...
3
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2answers
495 views

Who discovered that electromagnetic wave doesn't need a medium?

I have read that physicists in 19 century searching for the aether. They thought that light must have some medium to carry. When did they know that light and other electromagnetic wave doesn't need ...
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1answer
96 views

Electromagnetic interaction physical interpretation [duplicate]

Why do radio waves, X-ray and gamma rays penetrate through matter? Can anyone explain me this in terms of incident energy or wavelength of the photon and the effective cross-section that these photons ...
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1answer
98 views

Why is a particular wavelength favored by transmission through a thin film?

A sheet of glass is coated with a $500\text{ nm}$ thick layer of oil ($n=1.42$). For what visible wavelengths of light do the reflected waves interfere a) constructively? b) destructively? ...
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2answers
87 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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35 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
33 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
36 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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0answers
104 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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0answers
44 views

Is a smartphone with a radar possible? [closed]

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
250 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
54 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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35 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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3answers
54 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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0answers
74 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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2answers
376 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 ...
2
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1answer
82 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 ...