A monochromatic point source of light O is seen through a rectangular glass block ABCD. Path of two rays in and outside the block are as shown in the figure below.
.
(i) Does the source appear to be nearer or farther with respect to surface AB?
(ii) How does the shift depend upon the thickness AD or BC of the block ?
(iii) Justify your answer in (ii) with the help of ray diagram.
(iv) For the same rectangular block which colour from the visible spectra will produce the maximum shift ?

Explanation

(i) The source will appear nearer to the surface AB.

(ii) The shift decreases or increases with the decrease or increase in the thickness AD or BC of the block.
(iii) The ray diagram shows that for the thickness AD, the image is at I. while for thickness AD. ( (iv) For the same rectangular block the refractive index of violet colour being most, the shift of violet colour would be maximum.