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Question: how come a photon can carry a variable amount of energy? (Layman here, I would have guessed that photons travel at the speed of sound, and are of fixe

Question: how come a photon can carry a variable amount of energy? (Layman here, I would have guessed that photons travel at the speed of sound, and are of fixed size and energy, like electrons.)

coremoff 5y ago
Photons are massless and hence always travel at the speed of light. Photons have a wavelength, and that determins their energy; photons of a same wavelength will all have the same energy; the photons discussed in this article have very short wavelength and very high energy (this energy is proportional to their frequency and inversely proprotional to their wavelength). Regarding electrons; electrons have mass, and they all have the same mass. They have energy associated with this mass, and they also have energy associated with their momentum, thus they don't all have the same energy.
- terofle 5y ago
  > and like all Bosons are massless and hence always travel at the speed of light Not every boson is massless and not every boson is travelling at the speed of light (because there are bosons with mass). Take for example the Higgs boson or the W-bosons.
  - coremoff 5y ago
    ah, thank you; I will correct above
ben_w 5y ago
Photons do indeed all travel at the same speed, but are not all the same size, and what affects their energy level is their wavelength. Shorter wavelengths have more energy per photon, so e.g. a photon of blue light has about half the wavelength of a photon of red light and twice the energy. I’m curious if you really meant “speed of sound” in your question? Photons all travel at the speed of light, which is quite a lot faster than the speed of sound. But I’ve seen this several times from different places, and never found out if it’s basically just auto-complete in the speaker’s mind, or a genuine misconception.
- reactspa 5y ago
  I meant speed of light. Yes. That was a typo / brain glitch. Thank you for your explanation, helped a lot.

Question: how come a photon can carry a variable amount of energy? (Layman here, I would have guessed that photons travel at the speed of sound, and are of fixed size and energy, like electrons.)

coremoff 5y ago

Photons are massless and hence always travel at the speed of light. Photons have a wavelength, and that determins their energy; photons of a same wavelength will all have the same energy; the photons discussed in this article have very short wavelength and very high energy (this energy is proportional to their frequency and inversely proprotional to their wavelength). Regarding electrons; electrons have mass, and they all have the same mass. They have energy associated with this mass, and they also have energy associated with their momentum, thus they don't all have the same energy.

terofle 5y ago
> and like all Bosons are massless and hence always travel at the speed of light Not every boson is massless and not every boson is travelling at the speed of light (because there are bosons with mass). Take for example the Higgs boson or the W-bosons.
- coremoff 5y ago
  ah, thank you; I will correct above

ben_w 5y ago

Photons do indeed all travel at the same speed, but are not all the same size, and what affects their energy level is their wavelength. Shorter wavelengths have more energy per photon, so e.g. a photon of blue light has about half the wavelength of a photon of red light and twice the energy. I’m curious if you really meant “speed of sound” in your question? Photons all travel at the speed of light, which is quite a lot faster than the speed of sound. But I’ve seen this several times from different places, and never found out if it’s basically just auto-complete in the speaker’s mind, or a genuine misconception.

reactspa 5y ago
I meant speed of light. Yes. That was a typo / brain glitch. Thank you for your explanation, helped a lot.