First order fringes being reflected back to the 0 order

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    First order Fringes
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Discussion Overview

The discussion revolves around the phenomenon of diffraction patterns created when first order fringes from a laser passing through a diffraction grating are reflected back towards the central point. Participants explore the validity of this concept and its experimental implications.

Discussion Character

  • Exploratory, Technical explanation, Experimental/applied

Main Points Raised

  • One participant questions the validity of the claim about creating a second diffraction pattern and seeks confirmation before conducting an experiment.
  • Another participant suggests that the reflected beam's angle should indeed produce fringes.
  • A participant inquires whether the equation d*sin(theta) = m(lambda) would still apply with a specific distance between mirrors, proposing a comparison to a double slit experiment.
  • Another participant notes that the inner rays have a shorter distance than the outer rays, implying that a stripe pattern will emerge, while also suggesting that the distance from the source to the mirror will affect the results.

Areas of Agreement / Disagreement

Participants express varying viewpoints on the expected outcomes of the experiment, with no consensus reached regarding the validity of the initial claim or the applicability of the diffraction equation in this context.

Contextual Notes

Participants have not fully resolved the assumptions regarding the experimental setup, including the specific distances and angles involved, which may influence the diffraction patterns observed.

cseanm
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I heard that if you put a laser through a diffraction grating, and then reflect the first order fringes back to the middle point you will create a second diffraction pattern within the bright spot you are creating. I have been asked to try to test this and would like to know whether or not it is true before spending time trying to get the experiment to work correctly (I briefly tried and could not see any diffraction pattern whatsoever).

Thanks!
 
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The reflected beam is coming in at an angle, so I think there should be fringes.
 
So, if the mirrors were 5cm apart would the equation d*sin(theta) = m(lambda) still work for the new fringes created? With d now being 5cm?

ie, would it would turn into something similar to a double slit experiment, just with light sources quite far apart and distance between the fringes extremely small?
 
The inner rays have a shorter distance then the outer ones, so you should get a stripe pattern. The result will differ a bit from the double slit I think, because the distance from the source to the mirror is also relevant. If you split a beam in two parts and let one beam interfere with the other beam at an angle this will always produce stripes.
 

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