Effect of source slit in Young's Double Slit Experiment

In summary, when the source slit is moved closer to the double slit plane in Young's Double slit experiment, the interference fringes become less defined due to decreased spatial coherence of the light arriving at the double slits. This is a classical wave optics phenomenon and is not specific to quantum optics. Additionally, the condition s/S <= λ/d must be satisfied for the fringes to appear, where s is the size of the source slit, S is the distance of the source slit from the double slits, λ is the wavelength of the source light, and d is the distance between the double slits.
  • #1
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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  • #2
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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  • #3
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.
 

1. What is Young's Double Slit Experiment?

Young's Double Slit Experiment is an experiment that demonstrates the wave nature of light. It involves a light source, two parallel slits, and a screen.

2. How does the source slit affect the results of the experiment?

The source slit controls the width and intensity of the light waves passing through the two slits. A narrower source slit will produce a more focused and brighter interference pattern, while a wider slit will produce a less defined and dimmer pattern.

3. What happens when the source slit is widened or narrowed?

When the source slit is widened, the interference pattern becomes less defined as the light waves become more spread out. When the source slit is narrowed, the interference pattern becomes more defined as the light waves become more concentrated.

4. How does the distance between the source slit and the two slits affect the results?

The distance between the source slit and the two slits determines the angle at which the light waves pass through the slits. A longer distance will result in a wider angle and a shorter distance will result in a narrower angle. This will affect the interference pattern on the screen.

5. Can the source slit be completely closed in the experiment?

No, the source slit cannot be completely closed because there needs to be some space for the light waves to pass through and create an interference pattern. However, if the source slit is made very small, it will have a similar effect to closing it completely.

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