Physics - Geometrical Optics Question with Solution | TestHub

Pulfrich refractometer is used to measure the refractive index of solids and liquid. It consist of right angled prism $A$ having its two faces perfectly plane. One of the face is horizontal and the other is vertical as shown in the figure. The solid $B$ whose refractive index is to be determined is taken having two faces cut perpendicular to one another. Light is incident in a direction parallel to the horizontal surface so that the light entering the prism $A$ is at critical angle $C$. Finally, it emerges from the prism at an angle $i$.\\

Let the refractive index of the solid be $\mu$ and that of the prism $A$ be ${\mu }_0$ (which is known). Here ${\mu }_0>\mu$ and by measuring $i$, $\mu$ can be determined.