'Mirage' is a phenomenon due to

$A$ green light is incident from the water to the air-water interface at the critical angle $(\theta)$. Select the correct statement.

$A$ ray of light is incident normally on one face of a right-angled isosceles prism. It then grazes the hypotenuse. The refractive index of the material of the prism is

$A$ wide container is filled with water $\left(\mu=\frac{4}{3}\right)$ up to a height of $1 \ m$. Find the diameter of the disc at the top of the water surface from which light is coming out.

The critical angle for diamond (refractive index $= 2$) is........$^o$

The velocity of light in a medium is half its velocity in air. If a ray of light emerges from such a medium into air,the angle of incidence,at which it will be totally internally reflected,is ......... $^o$