Skip to main content

Questions tagged [electromagnetic-radiation]

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

Filter by
Sorted by
Tagged with
0 votes
0 answers
30 views

Polarization of electric field and its effect on the Poynting vector

To preface, I've little experience with optics. This is a very use-case specific project I'm undertaking. So, if there are any improvements in my method, I'd appreciate it! I'm working with the vector ...
sphericalcow's user avatar
0 votes
0 answers
28 views

How does an electromagnetic wave behave when it enters a medium with refractive index less than unity?

From what I am able to find, the phase velosity of the wave exceeds c, but the group velosity remains less than c. However, why does the wave form wavepackets after entering a medium with refractive ...
QuarkGP's user avatar
  • 11
0 votes
0 answers
75 views

Problem with Bohr Frequency in Quantized Radiation - Matter interaction

Consider an Hydrogenic Atom (no relativistic corrections and no reduced-mass effects) in a Quantized Electromagnetic Pulse given by the wave-packet: $$ \underline{\hat{A}}(\underline{\hat{r}}, t) = \...
Matteo Menghini's user avatar
0 votes
0 answers
23 views

On dimensions as a concept [duplicate]

really naive question here, i don't know anything about physics, in a professional sense. Light is a electromagnetic wave, and itself requires 3 dimensions to propagate, then how can a one-dimensional ...
Aditya Mishra's user avatar
0 votes
1 answer
41 views

Is amplitude measured from the electric or magnetic fields of a wave?

When you measure amplitude, does that refer to the electric portion of the electromagnetic field, or does it refer to the magnetic portion? Or is an average of the two? Another question is, are the ...
Astrovis's user avatar
  • 187
1 vote
1 answer
45 views

Imhomegenous Wave Equation: Possible Born and Wolf Error

My concern involves the following lines from Principle of Optics (Born and Wolf 7th ed, 60 year anniverary, Section 1.2 pg 11). I fail to derive these equations 5,6 exactly. $$ \begin{align} \nabla^...
Fredrik Sy's user avatar
-2 votes
1 answer
55 views

Can light propagate in the absence of electric and magnetic fields?

It has been established that light or other forms of electromagnetic radiation needs electric and magnetic fields in order to propagate. What would happen if it were possible to shield an area from ...
Dilip James's user avatar
2 votes
1 answer
48 views

Physics behind Lambertian reflectors

Most ordinary surfaces are near Lambertian diffuse reflector, i.e. a small local radiates most strongly at norm then attenuates by cosine law when one gets to the tangentials. However this seems hard ...
Meatball Princess's user avatar
1 vote
1 answer
54 views

"Residence time" of a photon?

E.g. CO2 absorbs and emits electromagnetic radiation at some frequencies. If the CO2 molecule is in a continuous electromagentic field, it will absorb and emit. What is the time between absorption and ...
Jonas's user avatar
  • 19
0 votes
2 answers
289 views

Solving the Inhomogeneous Wave Equation

This question is based on a problem from JD Jackson's Classical Electrodynamics, which asks for the solution of the inhomogeneous wave equation: $$\frac{1}{c^2} \frac{\partial^2{A^{\nu}}}{\partial t^...
V Govind's user avatar
  • 442
0 votes
0 answers
24 views

Stimulated emission semiclassical model for atom recoil

In the context of Saturated absorption spectroscopy, I'm having trouble modeling stimulated emission, and getting the result that is written in articles, such as this article. I tried to use a non-...
Doron Behar's user avatar
0 votes
2 answers
82 views

Black Body radiation and radiation in general [duplicate]

So I'm learning about blackbody radiation and radiation in general. As I understand it, there are 3 ways to transfer energy/heat: Convection, Conduction and Radiation. In chemistry I also learnt about ...
user15755358's user avatar
1 vote
1 answer
61 views

In Rayleigh-Jeans radiation law, why are the values of $n$ taken to be non-positive only?

In $k$-space the allowed values for standing waves in a cube of side length $L$ are given by $$\vec{k} = \left(\frac{\pi}{L}\right) (n_1, n_2, n_3)$$ where the $n_i$ are nonnegative integers. Why are ...
iman Bilal's user avatar
3 votes
2 answers
134 views

Why is $c = \frac{1}{\sqrt{\mu_0 \epsilon_0}}$?

I'm sorry if this is a duplicate but I didn't find my answer. I'm currently studying maxwell's equations and I know that by comparing the wave equation for either the magnetic or the electric field \...
Axodarap's user avatar
0 votes
0 answers
52 views

Difference between the spectrum of hydrogen and black body radiation [duplicate]

So I'm learning about blackbody radiation and radiation in general. As I understand it, there are 3 ways to transfer energy/heat: convection, conduction and radiation. In chemistry I also learnt about ...
user15755358's user avatar
1 vote
1 answer
26 views

Spectroscopy on colored flames

When observing colored fire through a spectrometer after adding substances like copper chloride or magnesium sulfate to change its color, what specific spectra are typically observed? How does the ...
Rookynote's user avatar
1 vote
0 answers
22 views

Understanding and researching with Spectroscopy

I am very new to physics so don't know a whole lot yet, so please correct any incorrect vocabulary you may find. Papers that are easy for beginners to understand are also very welcome! Context: I am ...
Rookynote's user avatar
3 votes
2 answers
124 views

Are EM waves telling us the probability of finding a photon?

I feel like I've been frequently presented with an interpretation of EM waves that goes something like this: Light is an oscillating electromagnetic field. Because changes in the electric field ...
Chris Gnam's user avatar
0 votes
1 answer
39 views

What determines the wavelength in absorption?

When looking at absorption or reflectance spectra, say in the range of 400nm to 2500nm, you can see peaks (or dips) at certain wavelengths, that are characteristic for the material absorbing and ...
YPOC's user avatar
  • 111
0 votes
1 answer
66 views

Direction of propogation of a EMW [closed]

If let say i have an EMW given by- (Note the difference between $k$ and K) B(x,y,z)=$B_0sin[(x+y)\frac{K}{√2}+wt]\hat k$ i got confused in 2 different outcomes when i wanted to find out the direction ...
SHINU_MADE's user avatar
0 votes
0 answers
45 views

Electromagnetic entropy maximum in Planck's black-body radiation law

I am reading Planck's work on black-body radiation. In the paper on the page 19 it is said that the expression $$R_\nu=\frac{\nu^2}{c^2}U\tag1$$ where $R_\nu$ is the intensity of a linearly polarised ...
User198's user avatar
  • 443
0 votes
1 answer
58 views

Why is red the brightest in the emission spectra of Hydrogen Gas?

I was studying a very simplified intro to Spectroscopy. The following diagram shows the emission spectra of Hydrogen Gas: Credit: NASA, ESA, and L. Hustak (STScI) My Question: In the spectra, the ...
Golden_Hawk's user avatar
  • 1,064
15 votes
6 answers
7k views

Why color depends on frequency and not on wavelength? [duplicate]

To explain my question lets consider this example: The wavelength of light in a medium is $\lambda=\lambda_{0}/\mu$, where $\lambda_{0}$ is the wavelength in vacuum. A beam of red light ($\lambda_{0}=...
Devansh Mittal's user avatar
1 vote
0 answers
36 views

How to calculate vector potential $A$ from electric field $E$ in the field of strong field approximation? [closed]

In order to simulate higher harmonic generation (HHG) using the strong field approximation (SFA), we need to calculate vector potential $\textbf{A}$ from the electric field $\textbf{E}=E_{0}f(t)\cos(i\...
Dennis Luo's user avatar
0 votes
1 answer
65 views

Electromagnetic Dipole Radiation Derivation

I was reading this wikepedia page, about the dipole radiation, and I was wondering how to derive the $\mathbf E$ and $\mathbf B$ fields in this situation. I've started using the retarded potentials: $$...
Álvaro Rodrigo's user avatar
1 vote
1 answer
222 views

How did Fermi arrive at this particular expression of canonical conjugate?

Fermi (Quantum Theory of Radiation 1932), using the electromagnetic energy expression $W_e$, a new variable $v_s$ is derived in equation: $$v_s=\frac{\partial W_e}{\partial \dot{u}_s}$$ which is ...
Jyotishraj Thoudam's user avatar
3 votes
1 answer
130 views

How exactly classical electrodynamics fails to explain the Compton effect?

EDIT: This is a more precise version of an old post Classical Theory explanation of Compton Effect by someone else. Standard textbooks explain the Compton effect using the notion of photon. It is ...
MKO's user avatar
  • 2,226
1 vote
1 answer
55 views

Understanding radiation mechanism of inset fed microstrip antenna

I have designed a simple inset-fed microstrip antenna, resonating at 2.45 GHz. The transmission line model of the antenna reduces it to two radiating slots separated by a microstrip line, and it's ...
fraghotmailcom's user avatar
1 vote
0 answers
31 views

Why do light bulbs don't produce coherent waves? [duplicate]

My textbook says that light ways produced by light bulbs are not coherent but it doesn't describe the reason. I was wondering how could two waves not be coherent regardless of the source they are ...
Muhammad Ali's user avatar
2 votes
2 answers
96 views

Does gravitational lensing bend light of all wavelengths by the same amount?

Basically I am asking if gravitional lensing is bending or refracting light.
Michael Mcgarry's user avatar
7 votes
6 answers
4k views

Why does white light appear white?

When I think of white light, I'm imagining a combination of all 7 colors of light but I believe that since light has wave nature I can say that at some point that the probability density of red light ...
Gauransh's user avatar
10 votes
1 answer
740 views

On a tinted (reflective) window, why do I need to look from up close to see inside?

I've noticed that on a really tinted window, when looking from farther (and even pretty close just not touching the window), you cannot look inside, but when you put your head so close to the window, ...
Árpád Szendrei's user avatar
0 votes
0 answers
60 views

Effective aperture as a function of Azimuth and Elevation Angle

Wikipedia says The effective aperture of an antenna is given by $$A_{\mathrm{e}}(\theta, \phi)=\eta A \cos \theta \cos \phi ,$$ where, $(\theta, \phi)$ are the azimuth and elevation angles relative to ...
wanderer's user avatar
  • 101
0 votes
1 answer
52 views

Mach Zehnder Do-it-yourself

I have a red laser and BS. Can I make MZI at the lab? I heard that is very difficult to achieve the calibration. What is expected to be seen after BS2? A dark spot at centre with fringes around? I ...
Mercury's user avatar
  • 651
0 votes
2 answers
84 views

Emission of a single photon

When a single photon is emitted as a result of an electronic transition, it will have a defined energy and wavelength. However, its amplitude is not constant over infinite space and time; instead, it ...
QuantumQuasar's user avatar
0 votes
1 answer
67 views

Paradox in the observation of ripple

What I am going to speak about may not be a paradox but i see a contradiction here so I used used the word "paradox". To begin with, let there be 2 charges A and B which are stationary with ...
Sanjoy Kundu's user avatar
0 votes
0 answers
15 views

Track an object velocity in a 2D plane

I would like to track the motion (actually, I am more interested in the velocity) of an object in a 2D plane (typically 4m x 4m). The object speed is typically 10cm/s, but the mouvement may be chaotic ...
Majorana's user avatar
13 votes
1 answer
3k views

Why aren‘t other metals colored?

From an online lecture, I heard that $d$ orbitals cause metals to have a peak in their reflectivity curve at some wavelength. This is generally the case for most metals. However, the peak lies mostly ...
shar's user avatar
  • 167
1 vote
0 answers
106 views

The speed of light in medium with different frequency

We know that the speed of light in vaccuum can be expressed as $c=\frac{1}{\sqrt{\mu_0\epsilon_0}}$ and thus the speed of light in vaccuum is thus $$v=\frac{1}{\sqrt{\mu\epsilon}}=\frac{c}{\sqrt{\...
Pck Tsp's user avatar
  • 83
1 vote
3 answers
64 views

Does infrared radiation emitted by an object happen only from its surface, or is emission also from the centre of the object?

Textbook answer of how radiation is emitted is from the surface. Does the inside of a object also emit infrared?
xifus's user avatar
  • 11
1 vote
1 answer
125 views

Can an electromagnetic wave be polarised in the direction it propagates?

Can the electric field vector of an EM wave oscillate in the propagation direction? In text books the polarisation is always orthogonal to the propagation direction. I'm wondering specifically ...
Jorge's user avatar
  • 21
0 votes
3 answers
218 views

Is heat basically infrared?

Particularly given the fact that heat can propagate through a vacuum in the form of infrared radiation. But is the modern theory of heat based on the notion that heat in the matter(regardless of its ...
Mr X's user avatar
  • 439
-1 votes
1 answer
127 views

How big is light pressure as a fraction of light energy?

Light hitting a surface impart a force on the surface, often called "radiation pressure". My question is, given a perfectly reflective surface, if light hits it at 90° to return in the ...
Qwertie's user avatar
  • 195
1 vote
1 answer
50 views

Huygens Light Theory using Spheres and Miller's recent discovery?

Huygens writes in "Treatise on Light" a theory that propagation of light through the aether can be explained using Spherical waves emanating from every point and they interfere. Miller ...
Nick's user avatar
  • 245
0 votes
1 answer
62 views

Solving Maxwell Equations when a charge is put inside a generic conductor

A net point-charge density $\rho_0$ is impressed without speed (no impressed current density) at position r0 at time $t_0$. Relaxation analysis tells us the charge density will decrease exponentially ...
Kinka-Byo's user avatar
  • 1,319
1 vote
3 answers
236 views

What is the difference between photons and electromagnetic waves?

Electromagnetic waves are generated by accelerating electric charges. Photons on the other hand, tend to describe something different, specifically the particle nature of electromagnetic waves as ...
Blacklight MG's user avatar
0 votes
1 answer
66 views

What is the significance of "oscillating" electromagnetic waves as compared to other disturbances?

When we speak of electromagnetic waves, we think of oscillating waves. But all disturbances need not be oscillating at a frequency. For example, if I take water, I could just lower the bottom plate ...
Blacklight MG's user avatar
0 votes
0 answers
44 views

What is the origin of energy emitted as radiation by an electrically charged object stationary around a massive object?

Einstein's special relativity tells us that laws of physics are the same in all intertial frames. General relativity futher extends this by stating that reference frames that are in free fall around ...
juhist's user avatar
  • 123
6 votes
3 answers
711 views

Can you have diffraction without a slit, simply by reducing the size of light source?

Since the diffraction pattern only depends on the width of the slit and the wavelength of light, could we see a diffraction pattern if we use an extremely small (to the order of micrometers) light ...
Dumber Everyday's user avatar
0 votes
2 answers
124 views

Does gravity affects electromagnetic waves? Or electromagnetism affects gravity?

I'm confused about the relationship of electromagnetism and gravity, or are they even related? It has been said the electromagnetic field produces a gravitational field, and so, there is no gravity if ...
Unknown Ymous's user avatar