A point source of light O of single colour is seen through a rectangular glass slab PQRS. The paths of two rays, in and outside the slab, are shown in figure. In the diagram, label the position I of the source O where it will appear when seen through the surface RS. (ii) Does the source O appear to be nearer or farther with respect to the surface PQ ? (iii) How does the shift depend on the thickness PS or QR of the slab? (iv) Justify your answer in (iii) with the help of an appropriate ray diagram. (v) For the same rectangular glass slab, which colour from the visible spectra (violet to red) will produce the maximum shift ?

A point source of light O of single colour is seen through a rectangul

1.	A point source of light O of single colour is seen through a rectangular glass slab PQRS. The paths of two rays, in and outside the slab, are shown in figure. In the diagram, label the position I of the source O where it will appear when seen through the surface RS. (ii) Does the source O appear to be nearer or farther with respect to the surface PQ ? (iii) How does the shift depend on the thickness PS or QR of the slab? (iv) Justify your answer in (iii) with the help of an appropriate ray diagram. (v) For the same rectangular glass slab, which colour from the visible spectra (violet to red) will produce the maximum shift ?
Answer» Solution :(i) In FIGURE, I is the position of source O when seen through the surface RS. (ii) The source O appears to be at I, nearer with respect to the surface PQ when viewed through the surface RS. (iii) The shift OI decreases with the decrease in thickness PS or QR of the slab. (IV) The ray diagram is SHOWN in figure in which for the thickness PS, the image is at I, while for the thickness PS.( (v) The same rectangular glass slab will produce the maximum shift for VIOLET light incident on it for which the refractive index of glass is most.