Question

Question #f3082

Answer 1

`61^o`

Explanation:

Find the refractive index of the plastic:
`n_1 times sin theta_1 = n_2 times sin theta_2`

`n_1 times sin 30^o = 1 times sin 35^o`
`n_1 = (sin 35^o)/(sin 30^o) = 1.147`

The critical angle is found when the angle of incidence is large enough to make the angle of transmission equal to `90^o`.

Therefore, going from plastic to air:
`1.147 times sin theta = 1 times sin 90^o`
`sin theta = 1/1.147`
`theta = sin^-1 (1/1.147) = 60.7^o`