Question

When measuring the critical angle, in which medium do we need the refracted ray to be (air or glass)

Answer 1

Answer:

N1 sin theta1 = N2 sin theta2       Snell's Law

For the refracted ray to be reflected then sin theta2 = 1

N1 sin theta 1 = N2

Also N2 must be less than N1 for complete reflection

sin theta1 = N2/N1

If you are considering air and glass then N2 = 1   (for air)

sin theta1 = 1 / N2    where N2 must be for glass in this case