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 be viewed from the same point through a `15 cm`. Thick glass slab held parallel to the table ? `mu` of glass `1.5` Does the answer depend on location of the slab ?

Explanation

Actual depth of the pin, d=15 cm
Apparent dept of the pin =`d^(')`
Refractive index of glass, `mu=1.5`
Ratio of actual depth to the apparent depth is equal to the refractive index of glass. i.e.
`mu=d/d^(')`
`therefore d^(')=d/u`
`=15/1.5=10cm`
The distance at which the pin appears to be raised = `d^(')-d`
`=15-10 = 5cm`
For a small angle of incidence, this distance does not depend upon the location of the slab.