Question

Question #2cd1b

Answer 1

Snell's Law can be used to calculate the critical angle for total internal reflection.

`n_1 sin theta_1 = n_2 sin theta_2`

where `n_1` is the index of refraction of the incident substance
`theta_1` is the unknown critical angle
`n_2` is the index of refraction of the refracting substance
`theta_2` is the angle of refraction (`theta_2 = 90^o` in a critical angle question)

Isolate `theta_1` by dividing both sides by `n_1`

Then once you have solved for `sin theta_1`, remember to take the inverse sine to find the angle of incidence.