Solution: ① The optical path is as shown in the figure, and the total reflection occurs at point n, ∠ Mo ′ n = 30, and the critical angle C = 30 due to the geometric relationship.
From the law of refraction: sinc =1n.
de:n = 1 sinc = 1 sin 30 = 2。
(2) Let the distance between o and m be d, and the geometric relation sinc = dr.