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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Why is not everything transparent? [duplicate]
There is a related question on this site here: Why glass is transparent? Which explains that glass is transparent because the atoms in glass have very large energy differences between energy levels ...
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Can an LC oscillator be used to generate visible light?
The LC oscillator is most commonly used to generate radio waves for practical use and the frequency $\omega$ of the LC oscillator equals that of the electromagnetic wave so produced. So, can they in ...
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What is light, and how can it travel in a vacuum forever in all directions at once without a medium?
I know there are many questions that are similar (maybe identical?). I am not a physicist nor a student - I am just interested in physics and have been watching many physics channels on youtube ...
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Why is the photon emitted in the same direction as incoming radiation in Laser?
When an atom “lases” it always gives up its energy in the same direction and phase as the incoming light. Why does this happen? How can this be explained?
How does the photon generated because of ...
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What exactly are light waves?
We know a sound wave is a disturbance that moves through a medium when particles of the medium set neighboring particles in motion. And using the pressure variations we can plot a
pressure/time graph ...
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Are there weak force waves?
In the same way as there are electromagnetic and gravitational waves that update the information on their respective field, is there an analogue for the weak and strong forces?
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What's the difference between Hard X-rays and Gamma-rays?
So I'm aware of this and this, but the question is Are Hard X-rays and Gamma-rays the same thing?
If not, then what would be the key difference between them. Moreover, How much would the properties of ...
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Interesting relationship between diffraction and Heisenberg’s uncertainty principle?
I recently came across an interesting explanation of diffraction through an aperture which does not use Huygens’ construction but instead relies on Heisenberg’s uncertainty principle:
The uncertainty ...
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Why is the atmosphere transparent in the visible spectrum?
One of the great 'coincidences' in physics is that the Sun happens to shine most brightly at exactly the wavelengths our eyes can see; it's an easy explanation that our eyes evolved to make the most ...
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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 oscillating ...
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Maximum wavelength of a photon/electromagnetic radiation?
This asked:
What is the minimum wavelength of electromagnetic radiation?
And also this:
What is the maximum possible frequency and wavelength?
The second question is contradictory; maximum ...
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Induction and electromagnetic fields
I've got a few questions on induction and electromagnetic fields. My current understanding of induction and electromagnetic fields is that, when electricity/current flows through a wire, it creates an ...
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Electromagnetic Momentum
My book says : The fact that electromagnetic radiation of energy carried momentum was known from classical theory and from the experiments of Nichols and Hull in 1903. This relation is also consistent ...
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What makes the radiation behind slits coherent?
Have a look on the sketch
To get such a intensity distribution of light behind a slit we presuppose that all the light that moves on the two lines is coherent; of the same wavelength AND the same ...
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Why do light disappears the moment we switch off the source (inside the wooden box)?
I am failing to explain why light won't remain inside the wooden box in the following situation. I considered a wooden box closed from all the sides, with a bulb inside it. If we switch on the bulb, ...
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Question about intensity of EM waves
For electromagnetic wave if it's reflected from a perfect conductor standing wave can be form. I wonder why Poynting vector can be used to describe the intensity of standing EM wave. (see p.19 of http:...
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Can electromagnetic fields be used to deconstruct and reconstruct atoms?
I was thinking one day and came up with a theory after reading about how scientists were studying anti-matter by using electro magnetic fields to separate matter from the anti-matter they made. It ...
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Can a photon get emitted without a receiver?
It is generally agreed upon that electromagnetic waves from an emitter do not have to connect to a receiver, but how can we be sure this is a fact? The problem is that we can never observe non-...
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How is the energy loss by an accelerating charge expressed in the equations of motion?
I understand how, and why, an accelerating charge emits radiation, and loses energy in the process, as well as the Larmor formula for the power, and its derivation.
However, in classical mechanics, ...
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How do you make a spherical radio wave?
A vertical rod, a usual dipole, produces radio waves in the horizontal plane, mostly in two opposite directions:
$\qquad \qquad \qquad \qquad \qquad $
If that is possible, how do you produce a ...
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Why doesn't the LHC accelerate electrons?
Electrons
have a much bigger charge density as the protons (and especially lead nuclei),
aren't compound particles as the protons (and especially lead nuclei)
are able to get a much bigger energy ...
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Is it possible to confine a photon in less than its* wavelength?
*(Its, or associated. That is somehow the question).
I can think of, at least in principle, a perfectly reflecting optical cavity with dimension comparable to the wavelength of the electromagnetic ...
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Is there any example where electric and magnetic fields are not perpendicular?
Perpendicular electric and magnetic field creates light or other electromagnetic waves. Is it a necessary property to have a perpendicular fields? If not what would happen when the fields are not ...
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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 ...
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Does a radio receiver "collapse" a radio wave function?
Does a radio receiver "collapse" a wave function when listening to a radio broadcast generated via a transmitting antenna?
Background:
There has been much discussion on this forum (here) ...
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How electromagnetic waves are created?
Macroscopically, electromagnetic waves are produced by a changing dipole or an oscillating charged particle as shown below:
In this case, the frequency of the electromagnetic radiation is equal to ...
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Can the question of a gravitationally accelerated charge radiation be tested experimentally?
I know that the question of radiation from a gravitationally accelerated charge has been discussed extensively at Does a charged particle accelerating in a gravitational field radiate?. Yet the ...
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What does a photon emitted by an atom "look" like?
Consider the emission of a photon when an atom decays from an excited state to its ground state. In most cases, this emitted photon is depicted as a small wave-packet being expelled by the atom in a ...
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Why are EM plane waves transverse?
I was reading Griffiths' Introduction to Electrodynamics, specifically Section 9.2.2 on plane waves. I can see that if we want a transverse wave traveling in the $z$ direction that we are only going ...
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Visualizing A Light Wave
I'm new to the forum. So I'm not sure how a question like this will be received, but it's a sincere question that I have wonder about often.
Let's say on a nice summer evening I shine a red laser ...
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If photons move linearly, what's actually stopping them from passing through a microwave oven mesh?
So, my understanding is that the wavelength of a photon is the distance traveled in the time it takes it's magnetic field to oscillate. And it's inversely proportional to it's energy and it's ...
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How is the path integral for light explained, or how does it arise?
In a Phys.SE question titled How are classical optics phenomena explained in QED (Snell's law)? Marek talked about the probability amplitude for photons of a given path. He said that it was $\exp(iKL)$...
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Do photons and cosmic rays radiate energy through gravitational waves? If not, why not?
Due to the mass-energy equivalence, both matter and EM radiation bend spacetime, and both are capable of forming singularities (black hole, white hole/kugelblitz). In light of this, why do photons ...
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Why are the $\mathbf E$ and $\mathbf B$ fields of an electromagnetic wave mutually perpendicular?
Why are the wave number $\mathbf k$ and the electric and magnetic fields $\mathbf E$ and $\mathbf B$ are perpendicular to each other?
I know it but I haven't thought about it deeply.
How can I prove ...
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Why aren't all photons virtual particles even in the "vacuum" of empty space? [duplicate]
I'm thoroughly confused about the nature of electromagnetic radiation. Light is supposed to exhibit both wave and particle characteristics. But does that mean that it is both a wave and a particle or ...
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Why there is electromagnetic resistivity $\approx 377\Omega$ in vacuum?
I cant understand that. If there isn't a material that makes it hard to pass, why there is a resistivity $\approx 377\Omega$ in vacuum?
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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 ...
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The energy of an electromagnetic wave
The intensity of an electromagnetic wave is only related to its amplitude $E^2$ and not its frequency. A photon has the same wavelength as the wave that's carrying it, and its energy is $h f$.
So ...
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How to imagine the electromagnetic waves? [duplicate]
I've learned at school, that the electromagnetic radiation consists of photons. And all the frequencies of the wavelengths of photons define electromagnetic spectrum. The lower wavelengths are ...
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Do Photons Move in a Wave Like Pattern? [duplicate]
In many pieces of literature, light is said to travel like a "wave". Does this mean the light literally propagates through space like a wave as in up and down and so on or does light move linearly ...
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Is spin necessary for electromagnetism?
I know that spin is needed for defining the magnetic moment of any particle, and I have also read that the spin actually is the reason why some materials are magnetic. What I want to know is whether ...
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Is the Speed of Light an universal spacetime constant, the velocity of electromagnetic waves, or of photons?
This question has been touched tangentially by What's a better phrase than "speed of light" for the universal spacetime speed constant? and Could light travel more slowly than the "...
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Does waving a magnet around create light?
If I wave around a bar magnet, the magnetic field in the space around it changes. Is this enough to go through the whole speed of light derivation implying that the motion creates an electromagnetic ...
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How do you calculate power at the focal point of a mirror?
I'm a Mechanical Engineering student and I'm working on my senior project, so I need help. My project is about designing a solar dish having a diameter of 1.5 meters and a focal length of 60cm. so at ...
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Planck's catastrophe?
In deriving Planck's blackbody formula, the number density of normal modes (per unit frequency$^\dagger$) is found, given by
$$
N(\omega)=\frac{V}{\pi^2c^3}\omega^2,
$$
where $V$ is the volume of the ...
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What is the maximum possible frequency and wavelength? [duplicate]
As a start I assumed Planck angular frequency which is the reciprocal of Planck time as the frequency upper limit, but not so sure. On the other hand, is there a lower limit? Can we consider the ...
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Do mechanical stresses propagate in time as EM waves do?
If someone may, I expect a mathematical comparison of the governing equations "Maxwell Equations" for wave propagation and "Conservation of momenta & equilibrium equations" for stress and ...
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If electromagnetic fields give charge to particles, do photons carry charge?
As I understand these two statements:
An electromagnetic field gives particles charge
A photon is a quantum of electromagnetic field
It must mean that a photon carries charge. But I guess it isn't ...
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Why doesn't an electromagnetic wave violate conservation of energy?
I'm starting to study electromagnetic waves and as i understand, an electromagnetic wave projects a varying electric field. This electric field can in turn give forces of repulsion/attractions to the ...
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