(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

Parallel light in air enters a transparent medium of refractive index 1.33 and is focused 35 mm behind the surface. Calculate the radius of curvature of the surface of the medium

2. Relevant equations

[itex]f = \frac{R}{2}[/itex]

[itex]\frac{1}{f}=(n-1) \left( \frac{1}{R_1}-\frac{1}{R_2} \right)[/itex]

3. The attempt at a solution

The correct answer must be8.68 mm, I can't see how they got this answer.

We know that the focus is 35 mm, so if we use the equation

[itex]R=2f=2 \times 35 = 70 \ mm[/itex]

But this is not correct and it doesn't take into account the refractive index.

So, I also tried using the lens-maker's equation:

[itex]\frac{1}{35} = (1.33-1) \left( \frac{1}{R}- 0 \right) \implies R = 17.9[/itex]

I wasn't sure what to use for the second radius so I used 0, and I didn't get the correct answer. So how can I get 8.68 mm?

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# Homework Help: The Radius of Curvature

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