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Newton's Ring Experiment

by ppdjoy
Tags: experiment, newton, ring
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Feb28-10, 03:51 PM
P: 2
1. The problem statement, all variables and given/known data

In a Newton’s ring experiment, a plano-convex glass (n=1.59) lens having diameter 12.6cm is placed on a flat plate as in the figure.

When 608nm light is incident normally, 6 bright rings are observed with the last one right on the edge of the lens, at r.

(a) What is the thickness of the lens?
Answer in units of m.

(b) What is the radius of curvature of the convex surface of the lens?
Answer in units of m.

(c) What is the focal length of the lens?
Answer in units of m.
2. Relevant equations

t = (2n-1)λ / 4

3. The attempt at a solution

I'm using the above formula. But for some reason, I keep getting the question wrong. I'm not sure if my approach is wrong or what.

Can anyone suggest me some methods as to how I should approach this problem? Like any different formulas or something?

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