# Thickness of thin lens [closed]

We have a double convex lens with optical power $D = 10$, $f\# = 2$, $n = 1.5$, and $r_1 = -r_2$. What is the minimum thickness of this lens?

I have a solution which is a bit convoluted, so I wonder if I am missing anything that would make it simpler.

From $D$, we have $f = 0.1$.

From $f\#$ and $f$, we have the diameter of the lens equaling $0.05$.

With LME, and $f$ and $n$, we have radius of curvature equaling $0.1$.

The only way I can think of getting thickness is from circular segment.

And solving for the sagitta, because we have the chord length (diameter of lens) and the radius of curvature. And the answer would be two times the sagitta.

This is my solution. I don't think we learned this in class. Is there a simpler way?

## closed as off-topic by John Rennie, sammy gerbil, Kyle Kanos, Yashas, Jon CusterDec 21 '17 at 8:45

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• I asked a friend how he solved it and he did the same thing. Go figure. I guess this way was correct – David Dec 21 '17 at 8:25