Question #f3082

1 Answer
Apr 14, 2017

#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#