Monochromatic light, Pattern on the screen

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Homework Statement:
Why is there a bright spot at its center? Thanks?
Relevant Equations:
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A point source of monochromatic light is placed in front of a soccer ball and a screen is placed behind the ball. The light intensity pattern on the screen is best described as:

Answer: a dark disk with a bright spot at its center and bright rings outside

Why is there a bright spot at its center? Thanks?
 

Answers and Replies

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kuruman
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That's Arago's spot. You get constructive interference from the diffracted rays at the edge of the sphere.

On edit: Here is what I consider a better picture than the Wikipedia article of a steel ball-bearing standing on a steel rod. The photo was taken with a green laser.

Arago.jpg
 
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  • #3
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That's Arago's spot. You get constructive interference from the diffracted rays at the edge of the sphere.

On edit: Here is what I consider a better picture than the Wikipedia article of a steel ball-bearing standing on a steel rod. The photo was taken with a green laser.

View attachment 277436
I got it! Thank you.
 

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