why the width of dark ring decreases as we go away from the center in Newton's rings experiment?
Hello and welcome to PF.
I will not give you the simple answer but you can maybe answer it yourself if you consider the following:
Why do you get cancellation at all? What is it about the separation of the two surfaces that makes it happen. How does the spacing between the two surfaces change as you move away from the contact point when one of the surfaces has a convex curve?
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