Why Does the Pattern Blur When I Approach in Young's Double-Slit Experiment?

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SUMMARY

The discussion centers on the phenomenon observed in Young's Double-Slit Experiment, where the interference pattern becomes blurry when a person approaches the setup. The participant noted that the clarity of the fringe pattern diminishes, potentially due to environmental factors such as air movement or temperature differences caused by body heat. The conversation also touches on the possibility that the fringes may appear clearer from a distance, suggesting that the perceived clarity is influenced by proximity. The inquiry seeks to understand the underlying physics and mathematical principles governing the intensity of the fringe pattern.

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jackiepollock
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Homework Statement
In the young double-slit experiment I have performed in lab today, I was to point the laser light through the double slits and observe the pattern formed on the screen. An interesting observation I found is that each time when my body come close to the pattern, it gets blurry. It changes from a clear pattern showing individual fringes to a hazy look in which the edges of fringes get blurred out. I tried it couple of times and it happens 6/10 times.
Relevant Equations
What might be the possible reasons for this blurry effect? Does the act of human bodies coming near the pattern affect the forming of the pattern?
As I searched online an answer suggested that the blurry effect might be a speckle pattern. However, it still hasn't explained the reason why when my body come near the pattern gets blurry.
 
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Could your footsteps on the floor, or the small wind created by your movement, have been making micro-movements in the apparatus?
 
Air movement from your movement or body heat? Especially if there are temperature differences within the room.
 
Hello @jackiepollock,

Welcome to PF! :welcome:

jackiepollock said:
Homework Statement:: In the young double-slit experiment I have performed in lab today, I was to point the laser light through the double slits and observe the pattern formed on the screen. An interesting observation I found is that each time when my body come close to the pattern, it gets blurry. It changes from a clear pattern showing individual fringes to a hazy look in which the edges of fringes get blurred out. I tried it couple of times and it happens 6/10 times.
Relevant Equations:: What might be the possible reasons for this blurry effect? Does the act of human bodies coming near the pattern affect the forming of the pattern?

As I searched online an answer suggested that the blurry effect might be a speckle pattern. However, it still hasn't explained the reason why when my body come near the pattern gets blurry.

Could it be that the fringe pattern was always blurry and that the individual fringes only appeared to be well defined when viewed from a distance -- similar to the way that it's difficult to tell that a blurry photograph is blurry if viewed from a distance?

What does that the mathematics say about the intensity of the fringe pattern? Does the math say that the individual fringes be well defined, or does the math show that the intensity pattern should be more sinusoidal-like?
 
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It is interesting experiment. I am looking forward to see the results of it. Thanks
 

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