$A$ point source of light is placed $4 \; m$ below the surface of water of refractive index $5/3$. The minimum diameter of a disc which should be placed over the source on the surface of water to cut-off all light coming out of water is ... $m$.

$A$ glass prism of refractive index $1.5$ is immersed in water (refractive index $\frac{4}{3}$) as shown in the figure. $A$ light beam incident normally on the face $AB$ is totally internally reflected at the face $AC$ to reach the face $BC$,if:

For total internal reflection to take place,the angle of incidence $i$ and the refractive index $\mu$ of the medium must satisfy the inequality

The critical angle of light passing from glass to air is minimum for which color of light?

Write the definition of critical angle.

$A$ glass slab has a refractive index ' $\mu$ ' with respect to air,and the critical angle for a ray of light going from glass to air is ' $\theta$ '. If a ray of light is incident from air on the glass with an angle of incidence ' $\theta$ ',then the corresponding angle of refraction is: