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## Homework Statement

The refractive index of diamond is 2.42. A ray of light passing from the inside of a diamond into air makes an angle of incidence of 20 degrees. Find the angle of refraction.

## Homework Equations

n = refractive index

aNd = 2.42 (my book said the speed of light in a vacuum and in air are close enough to treat them as the same for our purposes)

dNa = 1/aNd

Sin i / Sin r = dNa

i = 20 degrees

## The Attempt at a Solution

0.413 = dNa

Sin 20 degrees = 0.3420

0.3420 / sin r = 0.413

therefore 0.3420 x 0.413 = sin r

sin r = 0.142

arc sin of 0.142 = 8.159 degrees

This is wrong, the answer should be 55.9 degrees..

Where did I go wrong?

Did I go wrong in my maths or in my use of the formula?

If someone could point me in the right direction that would be wonderful.