Monochromatic light, Pattern on the screen

[hidemi]

Homework Statement

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

Relevant Equations

non

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?

 

[kuruman]

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.

 

[hidemi]

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.