Can Monochromatic Photons Exist in Electromagnetic Waves?

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Discussion Overview

The discussion revolves around the existence of monochromatic photons within electromagnetic waves, exploring the relationship between classical wave descriptions and quantum mechanics. Participants examine the implications of wave packets, group and phase velocities, and the conditions under which photons are considered monochromatic, particularly in the context of the photoelectric effect.

Discussion Character

  • Debate/contested
  • Conceptual clarification
  • Technical explanation

Main Points Raised

  • Some participants suggest that electromagnetic waves interacting at different frequencies create wave envelopes, which they refer to as photons.
  • Others argue that photons cannot be accurately described as wave packets and that a monochromatic photon, if it exists, would theoretically need to be infinitely spread out.
  • There is a discussion about the negligible frequency spread in practical light sources and its implications for the monochromaticity of photons in the photoelectric effect.
  • One participant questions whether a negligible frequency range could limit the spread of the group from infinity to a few nanometers.
  • Another participant clarifies that the few nanometers mentioned refer to wavelength spread rather than spatial spread, which must be at least on the order of a wavelength.
  • A different perspective is presented, suggesting that monochromatic light can be achieved through a complex process involving pinhole filters and prisms, conducted within a sphere to isolate the electromagnetic waves.

Areas of Agreement / Disagreement

Participants express differing views on the nature of monochromatic photons and the validity of mixing classical and quantum descriptions. No consensus is reached regarding the existence of monochromatic photons or the implications of frequency spread.

Contextual Notes

Limitations include the dependence on definitions of monochromaticity, the assumptions about the behavior of electromagnetic waves, and the unresolved nature of the relationship between classical wave theory and quantum mechanics.

sudu.ghonge
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When electromagnetic waves of different frequencies interact, they give rise to secondary wave structures called envelopes in which individual waveforms form at the rear and die out at the front. These envelopes are called groups and they travel with a velocity called group velocity and the individuals, phases and they travel with a phase velocity. These groups or envelopes are called photons right?
If so, can a photon of monochromatic EM wave exist? I recently studied that the wave function of a particle is the integral over a range of frequencies. This doesn't make sense because while studying the photo electric effect, we assume photons to be monochromatic.
 
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These groups or envelopes are called photons right?
You cannot mix classical wave descriptions and quantum mechanics like that. Photon can have some similarity to wave packets, but they do not have to. And wave packets can consist of many photons.
If so, can a photon of monochromatic EM wave exist?
Only in theory, it would have to be spread out infinitely.
This doesn't make sense because while studying the photo electric effect, we assume photons to be monochromatic.
Well, the frequency spread is negligible for appropriate light sources.
 
So what you're saying is that even a neglible frequency range is enough to limit the spread of the group from infinity to a few nm, right?
 
Those few nm are the spread in the wavelength, not any spatial spread. This has to be at least of the order of a wavelength.
 
Cant have monochromatic bc according to current theory em waves are going through everything so you can't have an isolated one.

That being said.

By passing light from a star through several pinhole filters (so that only rectilinear light goes through) and then through many prisms (to defract diferent light rays) and pick out one you are looking for, and then through pinhole filters again followed by many prisms and this process then repeated you will get a monochromatic em wave. Additonally you need to do this inside a conducting sphere so that other em waves don't cross inside.
 

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