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 having its two faces perfectly plane. One of the face is horizontal and the other is vertical as shown in the figure. The solid 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 is at critical angle . Finally, it emerges from the prism at an angle .\\
Let the refractive index of the solid be and that of the prism be (which is known). Here and by measuring , can be determined.
A ray of light incident normally on the horizontal face of the slab and just fail to emerge from the diagonal face of the prism. If prism angle refractive index of the prism is
Options:
Answer:
Solution:
The incidence angle at the diagonal face is .
The ray fails to emerge only if the incidence exceeds the critical angle: , i.e. ( is the grazing limit, not a failure).
So the prism index is slightly greater than .
