Light & Electron Energy: Comparing Quantized Energies

Click For Summary

Discussion Overview

The discussion revolves around the comparison of quantized energies of electrons and photons, exploring the nature of energy levels in both cases. Participants examine the implications of quantization in electron energy shells and the behavior of photon energies, particularly in relation to their interactions and the concept of continuous versus discrete energy levels.

Discussion Character

  • Exploratory
  • Debate/contested
  • Conceptual clarification

Main Points Raised

  • One participant questions how photon energies can be quantized like electron energies, given the perceived infinite number of intermediary frequencies between two light frequencies.
  • Another participant explains that light interacts in discrete amounts, termed "photons," which are proportional to their frequency.
  • A participant seeks clarification on whether photons can have any energy or if they are restricted to specific energy states like electrons.
  • It is noted that while photons can generally have any energy, those emitted from atomic transitions are limited to energies corresponding to the differences between specific energy levels.
  • One participant emphasizes that a photon has a single energy and cannot change its energy, although it can be absorbed and re-emitted as a different photon.
  • Another participant introduces the concept of gravitational redshift, referencing the Cosmic Microwave Background (CMB) and expressing confusion about the implications for individual photons.
  • A later reply suggests that the terminology in the CMB context may be misleading and proposes that the discussion should focus on radiation rather than individual photons.

Areas of Agreement / Disagreement

Participants express differing views on the nature of photon energies, with some asserting that photons can have any energy while others emphasize the quantized nature of photon emissions from atomic transitions. The discussion remains unresolved regarding the implications of gravitational redshift on individual photons.

Contextual Notes

Participants acknowledge the complexity of discussing photons, particularly in the context of gravitational effects and the terminology used in literature, which may not clearly convey the underlying physics.

Gabriel Hoshino
Messages
3
Reaction score
0
I was reading a section of a chemistry textbook describing electron energy shells. It compares the electrons to light saying that electrons energies are quantized and so are light energies. Electrons can only jump from one specific energy level to another with no intermediary energy levels. I understand that the same is true for the intensity of light, but I still don't understand how the energy of a photon can have only specific amounts of energy like an electron. Aren't there an infinite number of intermediary frequencies in between two frequencies of light? If that is true than doesn't that mean that the energy of photons doesn't skip around like the energy of electrons? Thanks.
 
Physics news on Phys.org
When light of a particular frequency interacts with anything, it transfers its energy in discrete amounts that are proportional to that frequency. We call this discrete chunks "photons".
 
But can photons have any energy, or are they like electrons where they can only skip between energy states?
 
In general, photons can have any energy. The light emitted by an incandescent light bulb contains photons with a continuous range of energies. Photons that are emitted by transitions between atomic energy levels in a specific type of atom (e.g. in a gas-discharge tube) can have only energies that equal the difference between two of the energy levels.
 
Gabriel Hoshino said:
But can photons have any energy, or are they like electrons where they can only skip between energy states?

Any given photon has only one energy (setting aside for now the phenomenon of gravitational redshift). You can absorb it and then emit another photon with a different energy, but you can't just change the energy of the same photon.

(I should add that we're on very shaky ground even talking about "the same photon" - these aren't like little teeny grains of sand with a distinct existence of their own)
 
Nugatory said:
You can absorb it and then emit another photon with a different energy, but you can't just change the energy of the same photon.

That is what I thought too, but the Wikipedia article on CMB says, "The photons that existed at the time of photon decoupling have been propagating ever since, though growing fainter and less energetic, since the expansion of space causes their wavelength to increase over time". I have been having trouble understanding the CMB on a per photon basis.
 
anorlunda said:
That is what I thought too, but the Wikipedia article on CMB says...

That's one of the gravitational red shift cases that I didn't want to mess with. :)

In fact, that wikipedia article might be improved if it didn't use the word "photon" in that context, just spoke of radiation propagating outwards and being redshifted.
 
Awesome, thanks for all of your responses!
 

Similar threads

  • · Replies 1 ·
Replies
1
Views
2K
  • · Replies 1 ·
Replies
1
Views
2K
  • · Replies 78 ·
3
Replies
78
Views
7K
  • · Replies 7 ·
Replies
7
Views
2K
  • · Replies 33 ·
2
Replies
33
Views
3K
  • · Replies 15 ·
Replies
15
Views
3K
  • · Replies 13 ·
Replies
13
Views
2K
  • · Replies 5 ·
Replies
5
Views
2K
  • · Replies 1 ·
Replies
1
Views
2K
  • · Replies 4 ·
Replies
4
Views
3K