All Questions
Tagged with electromagnetic-radiation photons
622
questions
209
votes
10
answers
270k
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If photons have no mass, how can they have momentum?
As an explanation of why a large gravitational field (such as a black hole) can bend light, I have heard that light has momentum. This is given as a solution to the problem of only massive objects ...
- 2,774
117
votes
9
answers
66k
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What is the relation between electromagnetic wave and photon?
At the end of this nice video (https://youtu.be/XiHVe8U5PhU?t=10m27s), she says that electromagnetic wave is a chain reaction of electric and magnetic fields creating each other so the chain of wave ...
- 1,681
84
votes
3
answers
10k
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Can photons be detected without being absorbed?
I am thinking about a detector that would beep if light passes through it. Is it possible?
- 841
70
votes
6
answers
12k
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Why isn't my calculation that we should be able to see the sun well beyond the observable universe valid?
I recently read an interesting article that states that a human being can perceive a flash of as few as 5 or so photons, and the human eye itself can perceive even a single photon. The brain will ...
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56
votes
3
answers
9k
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Why doesn't light affect a compass?
In our daily life a lot of photons of visible light, infrared and radio etc move around us. We know that light is an electromagnetic radiation. So why doesn't that electromagnetic radiation affect a ...
- 1,925
55
votes
5
answers
6k
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Scattering of light by light: experimental status
Scattering of light by light does not occur in the solutions of Maxwell's equations (since they are linear and EM waves obey superposition), but it is a prediction of QED (the most significant Feynman ...
- 7,737
54
votes
5
answers
9k
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Are there any theoretical limits on the energy of a photon?
Is there any lower or upper limit on the energy of a photon? i.e. does the mathematical framework we currently use to study photons blow up when a photon surpasses a certain upper limit of energy? (or ...
- 7,319
49
votes
8
answers
23k
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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
45
votes
3
answers
8k
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How does light re-accelerate after slowing down? [duplicate]
Light travels at speed x through a vacuum, and then it encounters a physical medium and slows down, only to leave the physical medium and re-enter vacuum. The speed of light immediately re-accelerates ...
- 411
45
votes
6
answers
7k
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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-...
- 1,141
42
votes
7
answers
5k
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Do nuclei emit photons?
Generally in text books they say that when a electron goes from high energy state to a lower energy state it emits photons.
My question is, it is possible that a proton that goes from high energy ...
- 445
39
votes
5
answers
9k
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Why doesn't light kill me?
Why does each individual photon have such a low amount of energy? I am hit by photons all day and I find it amazing that I am not vaporized.
Am I simply too physically big for the photons to harm me ...
- 369
34
votes
4
answers
21k
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Explain reflection laws at the atomic level
The "equal angles" law of refection on a flat mirror is a macroscopic phenomenon. To put it in anthropomorphic terms, how do individual photons know the orientation of the mirror so as to bounce off ...
- 697
33
votes
3
answers
5k
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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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- 447
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 ...
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