Effect of source slit in Young's Double Slit Experiment

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SUMMARY

The discussion focuses on the impact of moving the source slit closer to the double slit plane in Young's Double Slit Experiment. As the source slit approaches the double slits, it appears larger, resulting in decreased spatial coherence of the light reaching the double slits. This phenomenon is rooted in classical wave optics, not quantum optics. The condition s/S ≤ λ/d must be satisfied for interference fringes to be observable, where s is the size of the source slit, S is the distance from the source slit to the double slits, λ is the wavelength of the light, and d is the distance between the double slits.

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  • Understanding of classical wave optics principles
  • Familiarity with the Young's Double Slit Experiment
  • Knowledge of spatial coherence in light
  • Basic grasp of interference patterns and fringe formation
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  • Study the mathematical derivation of the condition s/S ≤ λ/d
  • Explore the concept of spatial coherence in more detail
  • Investigate the effects of slit width on interference patterns
  • Learn about the differences between classical and quantum optics
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Students of physics, educators teaching optics, and researchers interested in wave phenomena and interference patterns in light.

Raghav Gupta
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What is the effect on the interference fringes in Young's Double slit experiment when the source slit is moved closer to the double slit plane?
I have seen you people @DrChinese , @Cthugha , @bhobba helping in these kind of topic before.
Can you help here?
It would be great if others also can help.
 
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That single slit is used to produce spatial coherence in the light that arrives at the double slits:

http://electron6.phys.utk.edu/optics421/modules/m5/Coherence.htm

As you move that single slit closer to the double slits, it "appears" bigger from the point of view of the double slits, and the light arriving at the double slits becomes less spatially coherent.

This is a matter of classical wave optics, by the way. It's not specific to quantum optics.
 
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Thanks. I have only one last question related to this.
If the size of source slit is s and the distance of single slit(source slit) from double slits is S, then how the condition s/S <= λ/d must be satisfied for the fringes to appear?
Here λ is the wavelength of the source light and d is the distance between 2 double slits.
 

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