Question

A small pin fixed on a table top is viewed from above from a distance of 50 cm. By what distance would the pin appear to be raised if it is viewed from the same point through a 15 cm thick glass slab held parallel to the table? Refractive index of glass = 1.5. Does the answer depend on the location of the slab? 

Answer 1

Real depth = 15 cm, µ = real depth/apparent depth

⇒ 1.5 = 15/apparent depth

⇒  apparent depth = 15/1.5 = 10cm.

Distance through which the pin appear to be raised = 15 – 10 = 5 cm.

The answer is independent of the location of the slab.