What Are Co-Phasal Wave Fronts in Fizeau Interferometry?

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Discussion Overview

The discussion revolves around the concept of co-phasal wave fronts in the context of Fizeau interferometry, particularly focusing on the wedge problem. Participants explore the implications of wave phase relationships and path differences in interference patterns.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant questions the meaning of co-phasal wave fronts, suggesting it may imply that the waves have the same phase.
  • Another participant explains that co-phasal wave fronts occur when the lengths of two paths differ by whole wavelengths, leading to constructive interference.
  • Some participants clarify that wavefronts are planes perpendicular to the direction of propagation, indicating they are in phase and will interfere constructively.
  • There is a discussion about the angle dependency of the path difference in the Fizeau wedge interferometer, with multiple participants acknowledging this aspect.
  • One participant expresses uncertainty about the derivation of a final equation related to the discussion and requests additional context or resources.
  • A participant raises a concern about potential misunderstandings regarding how interference is generated, referencing the two-slit experiment as a foundational concept.

Areas of Agreement / Disagreement

Participants generally agree on the concept of co-phasal wave fronts and their relation to path differences, but there is ongoing debate about the specifics of how these concepts apply in the context of the Fizeau interferometer, particularly regarding angle dependency and the derivation of related equations.

Contextual Notes

Some participants note that the discussion may be hindered by translation issues, particularly regarding terminology like "pass difference" versus "path difference." Additionally, there are requests for further information and clarification on specific equations and diagrams.

Who May Find This Useful

This discussion may be useful for students and researchers interested in wave optics, particularly those studying interferometry and the principles of wave interference in varying geometries.

Ahmed123
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TL;DR
Question and discussion about wave fronts and phases of the rays at the Fizeau interferometer
I am studying Fizeau analysis for wedge problem. I reached to this part and I cant follow. I have two questions and any help will be appreciated
1) what is meant by co-phasal wave fronts? does it mean that they have the same phase? ( how can I Think about the wave fronts in this case)
2) why the pass difference between the two rays is calculated by this formula?

image.PNG

Thanks in advance
 
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Ahmed123 said:
TL;DR Summary: Question and discussion about wave fronts and phases of the rays at the Fizeau interferometer

what is meant by co-phasal wave fronts?
It means that the waves emerging along both paths are in phase. That will happen when the lengths of the two paths differ by a whole number of wavelengths. So the distance travelled in the diagram between the blue exit point and the red exit point will be one, two three . . . . whole wavelengths. The term is "Path Difference" and not 'pass difference' (translation problem, no doubt).

An easier example to start with is when the plates are parallel and the incident wave is plane; you get full addition, all over the emerging wave for one angle (say normal) and cancellation at another angle. Put the appropriate angles in your calculations and it should work for that.

PS it's always worth while looking at more than just one source to resolve this sort of confusion. There are dozens available. :smile:
 
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The wavefronts are planes perpendicular to the direction of propagation. This means that the wavefronts are in phase with each other, and they will interfere constructively.
 
gravisxv said:
The wavefronts are planes perpendicular to the direction of propagation. This means that the wavefronts are in phase with each other, and they will interfere constructively.
Where? It is angle dependent.
 
I'm not sure where they get the final equation without a bit more help. Is there any more text that you could copy here?
Is there a link to the whole text?
 
@gravisxv We may be talking at cross purposes. It isn't clear if you actually understand how interference is caused when two path lengths are involved. How familiar are you with the basic way in which the fringes are generated by the two slit experiment?
 
It is certainly angle dependent. I understand what you're telling, in the Fizeau wedge interferometer, the path difference between the rays depends on the angle at which they emerge from the wedge.
 
gravisxv said:
It is certainly angle dependent. I understand what you're telling, in the Fizeau wedge interferometer, the path difference between the rays depends on the angle at which they emerge from the wedge.
If you accept that, then how would you not get fringes?
The details of that equation under your quoted diagram would need some fleshing out. I asked you for more info or a link. Do you have it?

Alternatively, look for another source and we could discuss that. You can't expect a one stop shop on Google.
 

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