11
votes
Is a photon truly massless?
Although everyone has heard of the famous equation:
$$ E = mc^2 \tag{1} $$
few realise that this is a special case and applies only in limited circumstances. Specifically it applies only to a massive ...
- 358k
9
votes
Is a photon truly massless?
The correct version of your syllogism is:
$E=mc^2$ for a particle at rest.
For a photon, $E>0$.
For a photon, $m=0$.
The correct conclusion is that a photon can never be at rest.
- 15.9k
6
votes
Is a photon truly massless?
Light has inertia: it takes a force to change the direction in which they travel, and if you have a box with light bouncing around inside of it, it takes more force to change the speed of the box than ...
- 14k
6
votes
Could a single gamma ray photon break the Schwinger limit? If so, at what energy?
Consider an electorn-positron collision, and the subsequent production if photons. It is known that there must be at least two photons produced. This is because momentum must be conserved. In the ...
- 936
5
votes
Is a photon truly massless?
I like pictures, and the relevant picture is:
You can ignore the formulae, they are just high school trig, tho, so nothing prohibitive. (The do look bad, though, I think it's because they are crammed ...
- 35.4k
5
votes
Accepted
Does photocurrent depend on intensity or on number of photons?
You have it right.
You can idealize it as each photon kicks off one electron. (It might be really that each photon kicks off one avalanche.) So current is proportional to number of photons.
If the ...
- 41.1k
4
votes
Does photocurrent depend on intensity or on number of photons?
The current depends on the number of photons with high enough frequency(energy). 1 radio photon and 1 gamma photon will give you 1 electron, because gamma photon has enough energy to expell an ...
3
votes
Can photons interact with one another?
Photons can interact with each other. However, the interaction is very weak in the vacuum. I'm not sure this can be explained using a simple explanation from wave-particle duality. The full ...
- 460
3
votes
Photonic black holes
For the sake of argument, let us simplistically take the photon energy $E=hf$, and see what kind of black hole we get.
The Schwarzschild radius of a given parcel of energy $E$, which has an equivalent ...
- 9,500
2
votes
How is light interference explained with photons?
Now, if we model light as collections of photons, how is light interference explained?
It is explained the same as classically. Classically there is an electromagnetic field that obeys Maxwell’s ...
- 103k
2
votes
Accepted
Why does the up and anti-up quark combine into a pion and not a photon?
Particle annihilation occurs when a particle meets its corresponding antiparticle, converting their mass-energy into two photons.
This is a useful oversimplification. Even electron-positron pairs, ...
rob♦
- 91.5k
1
vote
Energy and momentum conservation for photon absorption
As you point out, not all of the energy of the photon goes into exciting the electron, Similarly when stationary atom emits a photon, some of the electon level enenrgy goes into the recoil kinetic ...
- 54.5k
Only top scored, non community-wiki answers of a minimum length are eligible