College Physics 10th Edition by Raymond Serway,Chris Vuille

Exercise 71

A flint glass plate ( n = 1.66) rests on the bottom of an aquarium tank. The plate is 8.00 cm thick (vertical dimension) and covered with water ( n = 1.33) to a depth of 12.0 cm. Calculate the apparent thickness of the plate as viewed from above the water. (Assume nearly normal incidence of light rays.)