A glass prism deviates the red and violet rays through $$9^{\circ}$$ and $$11^{\circ}$$ respectively. A second prism of equal angle deviates them through $$11^{\circ}$$ and $$13^{\circ}$$ respectively. The ratio of dispersive power of second prism to first prism is

An ink mark is made on a piece of paper on which a glass slab of thickness '$$t$$' is placed. The ink mark appears to be raised up through a distance '$$x$$' when viewed at nearly normal incidence. If the refractive index of the material of glass slab is '$$\mu$$' then the thickness of glass slab is given by

Converging or diverging ability of a lens or mirror is called

One of the necessary condition for total internal reflection to take place is

( $$\mathrm{i}=$$ angle of incidence, $$\mathrm{i}_{\mathrm{c}}=$$ critical angle)