MyNameIsYoda Posts: 1, Reputation: 1 New Member #1 Aug 24, 2009, 08:05 PM
Physic-Optics, finding refractive index
How do I find the refractive index of a plano-convex lens (in air) when given the focal length and radius of curvature?
 Unknown008 Posts: 8,076, Reputation: 723 Uber Member #2 Aug 25, 2009, 02:30 AM

Take a look here:
Focal length - Wikipedia, the free encyclopedia

The formula is :

$\frac1f = (n-1) $\frac{1}{R_1} - \frac{1}{R_2} + \frac{(n-1)d}{nR_1R_2}$$

Since your lens is a planoconvex one, I guess you'll have to take the other 'radius' to be infinite. Let the 'other radius', which is the flat part be R_2

$\frac1f = (n-1) $\frac{1}{R_1} - \frac{1}{\infty} + \frac{(n-1)d}{n R_1\infty}$$

$\frac1f = (n-1) $\frac{1}{R_1} - 0 + 0$$

$\frac1f =\frac{ (n-1)}{R_1}$

I'm not sure for that one though. :o

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