Light implying consistency between QM and SR

  • Context: Graduate 
  • Thread starter Thread starter DaTario
  • Start date Start date
  • Tags Tags
    Light Qm Sr
Click For Summary

Discussion Overview

The discussion revolves around the relationship between Special Relativity (SR) and Quantum Mechanics (QM), specifically focusing on the implications of the Doppler effect on the energy and frequency of electromagnetic radiation, such as photons from a laser beam, when observed from different reference frames.

Discussion Character

  • Exploratory
  • Debate/contested
  • Conceptual clarification

Main Points Raised

  • Some participants propose that the increase in energy of radiation with its frequency is implied by Relativity.
  • Others suggest that the relativistic Doppler effect should be considered to account for the correct increase in energy of photons.
  • A participant questions the relationship between Relativity and Planck's equation, E = hv, noting that Planck himself regarded his equation as a hint rather than a definitive answer to the black body problem.

Areas of Agreement / Disagreement

There is some agreement that Relativity implies an increase in energy with frequency, but the discussion remains unresolved regarding the implications of this relationship and its connection to Planck's equation.

Contextual Notes

The discussion does not clarify the assumptions regarding the conservation of photons or the specific conditions under which the relativistic Doppler effect is applied.

DaTario
Messages
1,097
Reaction score
46
Hi All,

Let me see if I can put my doubt in words appropriately...

Imagine a source of EM radiation, say a laser beam, and suppose you are running against the laser's direction, i.e., photons go to positive x and you to negative x direction, for instance.

From the POV of SR, light does not change its velocity, but there is Doppler effect and the transfer of momentum and energy (from light to you) increases.

From the POV of QM, there is also Doppler effect and Planck's equation E = hv introduces also an increase in the energy and momentum of the photon.

I am considering that there is conservation of number of photons produced by the source in this context.

Do these two effects rest harmonically on the top of the same physicist's desk?


In other words, if photons are to be considered roughly packets of EM radiation, whose number are conserved in going from one reference frame to another, and if its velocity does not change in going from one reference frame to another so it must be that the energy ought to increase with the frequency. Does it make sense?



Best wishes

DaTario
 
Last edited:
Physics news on Phys.org
Yes, it makes sense.
So what is your question?
 
My question is:

Does Relativity in itself imply the increase of energy of radiation with its frequency ?


And perhaps we should go beyond classical Doppler effect. Does relativistic Doppler effect accounts for the correct increase (with the frequency) in the energy of photons (EM packets of radiation) ?
Best wishes

DaTario
 
Last edited:
DaTario said:
My question is:

Does Relativity in itself imply the increase of energy of radiation with its frequency ?

yes, it does


And perhaps we should go beyond classical Doppler effect. Does relativistic Doppler effect accounts for the correct increase (with the frequency) in the energy of photons (EM packets of radiation) ?
Best wishes

DaTario

yes, it does
 
It seems quite strange, for if Relativity could have offered support to Planck's equation, E = hv, Planck, himself, wouldn't have said that his equation was just a hint that was capable to provide an answer to the black body problem. Do you know some reference to this result ?

Thank you in advance,

Best wishes

DaTario
 

Similar threads

  • · Replies 27 ·
Replies
27
Views
3K
  • · Replies 1 ·
Replies
1
Views
555
  • · Replies 17 ·
Replies
17
Views
4K
  • · Replies 4 ·
Replies
4
Views
2K
  • · Replies 2 ·
Replies
2
Views
1K
  • · Replies 14 ·
Replies
14
Views
3K
  • · Replies 34 ·
2
Replies
34
Views
4K
  • · Replies 128 ·
5
Replies
128
Views
8K
  • · Replies 13 ·
Replies
13
Views
3K
  • · Replies 11 ·
Replies
11
Views
3K