If the velocity of light in the first medium is $v_1$ and in the second medium is $v_2$,then the refractive index of the second medium with respect to the first medium is given by:

The frequency of a light wave in a material is $2 \times 10^{14} \ Hz$ and its wavelength is $5000 \ \mathring{A}$. The refractive index of the material will be:

Consider a light ray travelling in air incident into a medium of refractive index $\sqrt{2n}$. The incident angle is twice that of the refracting angle. Then,the angle of incidence will be

In the formation of a primary rainbow,the sunlight rays emerge at minimum deviation from a raindrop after:

On heating a liquid,the refractive index generally

$A$ beam of white light is partially reflected and partially refracted from a surface. The angle between the reflected and refracted light is $90^{\circ}$. The angle of refraction is $30^{\circ}$. The angle of incidence must be (in $^{\circ}$)