Question

Why there is a dark ring in newtons ring at point of contact?

Answer 1

HEY DUDE HERE IS YOUR ANSWER....
At the center the thickness of the air film formed between lens and glass plate is zero. Therefore , at the center the geometrical path difference between the rays incident and reflected from glass plate is zero,but due to reflection a path difference of (lambda/2) is introduced. This path difference gives distructive interference at the center and hence center is dark.
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