Questions tagged [electromagnetic-radiation]

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

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An answer to an old question about a derviation of Wien's displacement law without Planck's radiation law [closed]

A derivation based on Doppler's frequency shift and a heat engine can be found in an appendix to Max Born's "Atomic Physics".
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How are these expressions for blackbody spectral energy density established?

My first question regarding the following is: given that it is very close to 1 in the atmosphere, do we really need to consider the index of refraction in this context? In the article Radiation and ...
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If there is no perfect black body then what's the point of learning about it?

My question is simple if there is no perfect black body then what's the point of learning about it? Because definition of balck body goes like this A body which can absorb and re emit all kinds of ...
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How does interferometric SAR determine position of the reflecting object?

I'm interested to know how synthetic-aperture radar functions. The Wikipedia article for Synthetic-aperture radar, subheading Interferometry says: If the two samples are obtained simultaneously (...
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Total Energy of an electromagnetic wave

This question may sound stupid. But why when we calculate the total energy density (energy/volume), carried by an electromagnetic wave $u_T$, we add both $u_B$ + $u_E$. Where $u_B = \frac{B^2}{2\mu_0}...
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Why does light bend when it enters a medium?

I am asking this question after referring to @benjimin answers at Why does light bend? I found the same answer at wiki. But i found a video on youtube by doctor don (https://www.youtube.com/watch?v=...
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Current produced by EM wave in circuit

I have a specific question regarding the current produced by an EM wave interacting with a simple square circuit with constant resistance $R$. Let's say the EM wave can be explained by the simple ...
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What is the relationship between emissivity $\varepsilon$ and the imaginary part of relative permittivity constant $\epsilon^{''}_{\rm r}$ if any?

In terms of the Stefan-Boltzmann law a body that does not absorb all incident radiation emits less total energy than a black body and is characterized by an emissivity $0<\varepsilon <1$ such ...
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Do two antennas need to have the same range in order to communicate?

If one antenna has a range of say 200 feet and a second antenna has a range of only 20 feet, can communication still occur if the first antenna is outside the 20 feet range of antenna 2?
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Does frequency equal mass?

If e equals mass and if frequency equals energy then is it correct to conclude that frequency equals mass?
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A question concerning microwaves [duplicate]

Why can't microwave radiation travel travel through the microwave oven? I observed that the glass on the front of the oven has a fine mesh behind it, with holes placed in a way that allows the ...
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Thought experiment on temperature dependence of black body radiation

There's a very famous thought experiment that verifies the temperature dependence of blackbody spectra The proof first assumes that two blackbodies have different spectra and then shows that this ...
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On Kirchhoff's law of thermal radiation

I came across a seemingly simple derivation of Kirchhoff's Law: Consider two bodies A and B placed in a constant temperature enclosure, and B is a perfect black body. After some time both of them ...
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Force of photons from the Sun hitting a football field = weight of 1 dime?

I read, I think, some time ago that the "weight" of photons from the Sun hitting an area the size of a football field at noon on a sunny day would be about the "weight" of a dime? ...
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Is visible spectrum really a thing and why our eyes evolved to see only visible spectrum when its of no use to us unlike infrared?

Visible spectrum is a thing only for human eyes, when we think about it deeply, visible spectrum is a part of light just like any other, but what makes it important is that humans can only see it, but ...
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What's the physical origin of bound states in the continuum?

From my point of view, BICs are modes built by destructive interference. But I'm confused about the orgin of BIC, I have two questions: The differences between BIC modes and defect modes. It has ...
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How does light fill the entire universe? [duplicate]

Light is a particle and a particle is discrete. So say light is emitted from a star 7 billion years far, how is it possible that this light particle emitting from a star fills every point in the ...
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Why was Rutherford wrong and Bohr was right (then)?

I read that Rutherford was ruled out because he predicted that electrons revolve around the nucleus and Bohr stated that accelerating electrons emit electromagnetic radiation and should collide with ...
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Observing a very long pulse

In our lecture we are considering the special case of observing a very long pulse propagating through a dispersive medium. For some reason we say that the spectrum will then be spectrally very narrow ...
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Photoelectric effect and wave nature of light [duplicate]

We know that when a light of specific frequency is collided on the silicon metal plate electron released from it, this is the photoelectric effect This effect proves the particle nature of light , but ...
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Understanding the solution for the electric field wave equation

We do know that that transladed $\mathcal{C}^2$ functions are solutions to the wave equation, namely: \begin{equation} \ddot{f}(k\hat{z}-\omega t)=c^2\nabla^2f(k\hat{z}-\omega t) \end{equation} Which ...
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Ferrys black body and mass of photon

We know , the black body absorbs all the radiation . After the absorption of all the radiation, why does the mass of the black body increases? photons don't have mass then, how the mass of black body ...
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Absorption and re-emission of waves

How accurate is the slowing of electromagnetic waves in a medium to be caused by the absorption of the wave by an electron. And the electron re-emitting the waves. And therefore causing a delay in ...
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Why light comes from fire?

We know that light is produced when a charge particle accelerate. Fire doesn't have electric and magnetic field so how do light comes from fire
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Question about electromagnetic radiation

I was taught that , in a electromagnetic radiation , changing electric field is produced due to oscillation of charge this changing electric field give rise to 'changing' magnetic field and this ...
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Producing constant constant electric field [closed]

Can we create constant electric field using varying magnetic field? And also , How the varying magnetic field give rise to varying electric field not a constant electric field .
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When and how will charged oscillating pendulum in vacuum and Earth gravity stop?

Let's say there is a positively charged metallic sphere hanging on a thread in Earth's gravity and in vacuum. There is no electric field (except for the field from the sphere itself), no friction etc. ...
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How do EM TOF sensors work with relatively? [duplicate]

Lasers, radar, etc can use TOF to measure distance. Since lights speed doesn't change relative to speed of what ever creates it, how can TOF be measured accurately considering the earth is moving (...
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Interaction of EM radiation with atoms

I have a few questions on the different types of phenomena of light and matter interaction. I understand there are generally 5 types of ideas. Diffraction, reflection, absorption, emission and ...
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Do light particles have thrust? [duplicate]

I understand that nothing is faster than light and that it can not escape a black hole. However, light particles may be fast, but perhaps it can't escape a black hole due to it's lack of thrust power? ...
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Are there certain EM frequencies that are impossible to emit?

Every element has absorption lines. Is there some line which is not covered by anything else? Some strange gap in the universe?
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Electromagnetic radiation of dipole in the frequency domain

Recently I've met a formaula that says the radiation power of a dipole in the frequency domain is $I(\omega) = |\omega^2P(\omega)|^2$, where $\omega$ is the frequency of the radiation and $P(\omega)$ ...
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Em radiation incident on an atom

What happens when the EM wave is incident on a atom? Do the de-localized electrons in the atoms or the valence band electons move in the direction of the electric field? Also when the electrons move, ...
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Is slower light darker?

Consider for example, electromagnetic waves inside conductors. The speed at which an EM wave travels at can be a considerable fraction lower than C So my question is, If I were standing with my eyes ...
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Planck's law and CMBR

Rereading statistical mechanics notes, I was recently struck by a fact that seemed very surprising to me. In the notes I am reading, one derives Planck's formula for the energy distribution of photons ...
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Black body thermal radiation vs. the uniqueness of EM energy in Poynting's theorem

In this post Feynman is quoted stating that GR can potentially remove the inherent ambiguities implied by Poynting's theorem in the definition of EM energy density and energy flux. Given $u=\frac{1}{2}...
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Superposition of EM waves [closed]

The following travelling Electromagnetic wave $E_x=0, E_y=E_0 \sin{(\omega t -kx)}, E_z=-2E_0 \sin{(\omega t +kx)}$ is (A) Linearly polarised (B) Elliptically polarised (C) Circularly polarised (D) ...
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Would an EMP disable another EMP

So,I may be watching a marathon of some unnamed movie. One captain criticizes another for using an EMP to stop the advancing enemy machines. It left them defenseless. However, every ship in their ...
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Where did I misunderstand Lienard-Wiechert?

Here's my problem. Intensity of radiation follows an inverse square law with distance. https://byjus.com/physics/inverse-square-law/ Electromagnetic fields can be derived from the Lienard Wiechert ...
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Do microwave oven doors use specular reflection as shown in this video. If so, what allows light to ignore imperfections based on wavelength?

I will attempt to restate the question asked here in another way without as much rambling/thought process included, as the provided 'duplicate' was actually both linked and quoted in my OP, and did ...
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Confusion in the plane wave solution for the EM wave equation

When talking about the solution of the Wave Equation for the Electric Field: \begin{equation} \ddot{E}=c^2\nabla^2E \end{equation} One usually assumes a sinusoidal waveform and writes: \begin{equation}...
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Do microwave oven doors use specular reflection, if so, how does that occur in microwave vs visible light? [duplicate]

Please comment if you're gonna down vote so i can improve :) I have poured over a lot of resources in the past few hours but have been unable to reach a satisfying answer, this question is more about ...
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How does a photon heat something up? [duplicate]

In heating by radiation when a photon hits an object what exactly happens to cause the atoms and molecules to vibrate quicker? How does the atom absorb the photons energy? Please be as in depth as ...
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Which energy is lost by an oscillating charge?

Let us imagine a charged block connected to a fixed spring in gravity free space and in a complete vacuum (to avoid air drag) . Now if an external agent stretches the spring from its natural length ...
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Where does the energy from expanded light go? [duplicate]

The universe is expanding and light traveling through it also expands. Light with longer wavelengths have less energy so light is losing energy as the universe expands. Where does this energy go? Or ...
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Do photons go through one another?

I just read somewhere that sound could travel through light, and that it can travel even though photons go trought each other. So could anyone explain this to me if they have time?
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Why is circularly polarized light used for optical pumping?

Why not linearly polarized light or unpolarized light? Maybe I've misunderstood atom-light interactions, but I thought that an electromagnetic wave with the right energy incident on an electron ...
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Can we calculate energy of light using wave theory? And will it be the same as $E=h\nu$?

From wave theory we got that energy of wave is given by $E = \frac{1}{2} \epsilon |\vec{E}|^2$ and from particle theory $E=h\nu$. So can we use wave theory to calculate energy of wave?
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Formulate the equations that describe this transmission-line circuit (Veritasium's circuit)

My question Consider the following circuit. Two non-resistive long transmission lines ($R' = G' = 0 \text{ } \Omega$) , each of the same length $L$ and same inductance per unit length $L'$ and same ...

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