All Questions
31
questions
2
votes
1
answer
36
views
Why don't the delocalised electrons in a metal emit light when they hit an atom and change their velocity very quickly (i.e. accelerate)
We know that in metals there is a sea of delocalised electrons which can freely travel around the lattice of metal ions and that these delocalised electrons move around at large speeds, sometimes ...
- 531
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 ...
- 123
0
votes
2
answers
205
views
Energy of an electromagnetic wave
The total energy density $(U)$ of an electromagnetic wave is given by the equation
$$U=\frac{1}{2}\epsilon_0{E_0}^2+\frac{1}{2}\frac{{B_0}^2}{\mu_0}\tag{1}$$
Also quantum energy $(E)$ of a photon in ...
- 87
4
votes
3
answers
164
views
Origination of electromagnetic wave energy
Please correct me if I am wrong in my statements
While it is said that electromagnetic waves are formed by the oscillation (acceleration) of charges which forms 'kinks' in their electric field which ...
- 87
1
vote
3
answers
171
views
How to Measure Energy of a Electromagnetic Wave accounting also for frequency?
We know a way of measuring energy of a electromagnetic wave is the Poynting vector, which is independent of the frequency. But let's say we want to make two different electromagnetic waves, with ...
-1
votes
1
answer
69
views
Interpretation of watts per square meter for intensity of radiation
The energy that an electromagnetic field can deliver to a system is proportional to the square of the field. However, we use the terminology watts per meter square to represent the amount of energy ...
- 3
0
votes
1
answer
101
views
Is $∫ (1/2)εE^2 dV$ in the entire volume of rays propagation $= nhf$? [closed]
I asked it on ChatGPT but it gave kind of a mixed answer contradicting itself in the process several times here is some of it.
"Kushagra Singh:
~so you mean $∫ (1/2)εE^2 dV$ in the entire volume ...
- 19
1
vote
0
answers
47
views
Radiation from a moving charge particle in expanding universe?
Moving charged particles generally emmit energy in form of radiation.
Assume a charged particle that is situated in a zone that can join the Hubble flow and therefore starts moving away from us.
As it ...
- 2,462
1
vote
1
answer
77
views
How do we interpret $E=|\vec{p}|c$ in classical electromagnetism?
$$E=|\vec{p}|c$$
Can this relation be derived purely from electromagnetic theory?
I.e., is this a general statement about the EM field as whole and not just individual photons?
I.e.
$$\left(\frac{1}{2}...
- 6,636
-4
votes
2
answers
144
views
Isn't the concept of light against law of conservation of energy itself?
Let's say there's a light wave travelling in vacuum, and it travels forever because it does not hit any object in its way. This light ray will produce oscillating magnetic and electric fields, but ...
1
vote
1
answer
273
views
Do Electric fields really contain energy in them? [closed]
If we assume that energy was first absorbed by q1 and then released by it which then reaches q2 , the same as , electric field not being absorbable and somehow magically gives the energy to q2 and q1 ...
0
votes
0
answers
50
views
Where can I find the Bragg Curves for Heavy Particles?
The Bragg Curves are graphs plotting the energy loss of ionizing radiation (KeV/μm usually) on the y-axis during its travel through matter (distance travelled usually in cm) on the x-axis.
I can't ...
- 101
0
votes
1
answer
163
views
Poynting vector on the surface of an isolated system
We've an isolated system inside which currents and charges reside.
If the Poynting vector on the surface of the system is non zero, then there is energy exchange between the system and the ...
- 1,270
1
vote
1
answer
56
views
Magnetic and Electric energy for AC fields
In "Applied Frequency Domain Electromagnetics" (here the page) there are these two equations for the computation of the magnetic and electric energies stored in a certain volume $V_0$:
$$W_{...
- 1,319
10
votes
4
answers
3k
views
Standard formula for energy density of electromagnetic field
The formula for energy density of electromagnetic field in electrodynamics is
$$\frac{1}{8\pi} (\vec E\cdot\vec D+\vec B\cdot\vec H).$$
This formula appears in all general physics courses I looked at. ...
- 2,226