Question

A flint glass plate (n = 1.66) rests on the bottom of an aquarium tank. The plate is 10.00 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.)

Answer 1

Data

n₁ = 1.66, n₂ = 1.33,

We know that

Here R is infinity

let us use this to locate the final images of the two surfaces of the glass plate. First, find
the image the glass forms of the bottom of the plate.

Here p = 10.00 cm

This virtual image is 8.01 cm below the top surface of the glass of 20.01 cm below the water surface.
Next, use this image as an object and locate the image the water forms of the bottom of the plate.

i.e. 16.03 cm below the water surface.

Now find image the water forms of the top surface of the glass.

i.e. 9.02 cm below the water surface.

Therefore, the apparent thickness of the glass is