All Questions
Tagged with electromagnetic-radiation quantum-mechanics
408
questions
156
votes
1
answer
15k
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What is an "attosecond pulse", and what can you use it for?
The 2023 Nobel Prize in Physics was announced today, and it was awarded to Pierre Agostini, Ferenc Krausz and Anne L’Huillier, for
“experimental methods that generate attosecond pulses of light for ...
- 134k
49
votes
8
answers
23k
views
Amplitude of an electromagnetic wave containing a single photon
Given a light pulse in vacuum containing a single photon with an energy $E=h\nu$, what is the peak value of the electric / magnetic field?
- 1,056
31
votes
12
answers
7k
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Why is everything not invisible if 99% space is empty?
If every object is $99$% empty space, how is reflection possible? Why doesn't light just pass through?
Also light passes as a straight line, doesn't it? The wave nature doesn't say anything about its ...
- 435
29
votes
5
answers
35k
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What exactly is a quantum of light?
I am currently trying to learn some basic quantum mechanics and I am a bit confused. Wikipedia defines a photon as a quantum of light, which it further explains as some kind of a wave-packet.
What ...
- 495
25
votes
9
answers
6k
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Why does light travel in a straight line if the uncertainty principle is true?
I've asked this on different websites and never gotten an answer that a layperson can understand. Most people just say that light does not have a trajectory and then they do some hand waving. If light ...
- 361
25
votes
1
answer
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Why does the intensity of unpolarized light reduce to half after passing it through a polarizer?
When unpolarized light is polarized with two polarizers, the intensity becomes $I=I_0\cos^2(θ)$ (Malus's law). But when unpolarized light is polarized with only one polarizer, the intensity is reduced ...
- 383
20
votes
3
answers
3k
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"Red Hot" Objects & the Ultraviolet Catastrophe
It is common for introductory courses in quantum physics to justify the need for a new model with the ultraviolet catastrophe, but I cannot seem to grasp it.
The flaw in the Rayleigh-Jeans law ...
- 315
18
votes
1
answer
2k
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Relation between radio waves and photons generated by a classical current
Several questions have been posted on Physics SE regarding the relationship between photons and electromagnetic waves, and several good answers have been given. Some of those questions are listed ...
- 54.5k
17
votes
4
answers
3k
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Same photon or different photon?
Consider a typical optical focusing system: A small light source, then a collimating lens, then a focussing lens, and then a detector (e.g. CCD).
Assume that source intensity is so low that only one ...
- 1,034
17
votes
4
answers
3k
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Why do electrons tend to be in energy eigenstates?
An oft cited problem with the planetary model of hydrogen is that, if the electron were in fact classically orbiting the proton, then it would radiate away all of its energy and fall into the nucleus. ...
- 1,590
14
votes
4
answers
18k
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Why do atoms emit a certain colour of light? (The emission spectra)
We were taught about the emission spectra in class last year, but my teachers couldn't give me an answer to 'what determines the colour of light emitted?'. (they were giving me the answers to the ...
14
votes
2
answers
1k
views
Analytical solution of two-level system driving by a sinusoidal potential beyond rotating wave approximation
A quantum mechanical two-level system driven by a constant sinusoidal external potential is very useful in varies areas of physics. Although the widely used rotating-wave approximation (RWA) is very ...
- 873
12
votes
6
answers
8k
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Light's inverse square law: Does it require a minimum distance from the source?
Does the inverse square law begin to take effect the moment light leaves its source? For example, does light's intensity decrease, i.e. does the area in which the photons might land increase, at a few ...
- 539
12
votes
7
answers
3k
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Does the radio (between two co-moving astronauts) stop working when crossing the event horizon?
There are a lot of questions about crossing the EH (event horizon) of a black hole on this site.
Some of them suggest, that when you cross the horizon, nothing special happens, you don't even notice ...
- 29k
11
votes
4
answers
3k
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If a polarized light wave is indistinguishable from its original self after being flipped 180°, why doesn't a photon have a spin of two?
The spin of a photon has a counterpart in classical physics, it's polarization, right?
And if you spin a polarized light wave by 180°, (or pi radians), it is now the same as before, correct?
So why ...
- 4,509