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

AI Thread Summary
The discussion centers on the observation that the interference pattern in Young's double-slit experiment becomes blurry when a person approaches it. Possible explanations include the influence of micro-movements caused by footsteps or air movement from the person's body, which could affect the apparatus. There is also speculation that the fringes may always be somewhat blurry, with clarity only apparent from a distance. Additionally, the conversation touches on whether mathematical principles governing the intensity of the fringe pattern support the observed clarity or suggest a more sinusoidal appearance. Overall, the phenomenon raises intriguing questions about the interaction between physical presence and optical patterns in experimental setups.
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?
 
It is interesting experiment. I am looking forward to see the results of it. Thanks
 
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