$A$ medium shows the relation between $\sin i$ and $\sin r$ as shown in the graph. If the speed of light in the medium is $nc$,then the value of $n$ is:

$A$ 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 $^{\circ}$)

Monochromatic light is refracted from air into glass of refractive index $\mu$. The ratio of the wavelength of incident and refracted waves is

If $\hat{i}$ denotes a unit vector along the incident light ray,$\hat{r}$ a unit vector along the refracted ray into a medium of refractive index $\mu$,and $\hat{n}$ a unit vector normal to the boundary of the medium directed towards the incident medium,then the law of refraction is:

The refractive indices of glass and water with respect to air are $3/2$ and $4/3$ respectively. The refractive index of glass with respect to water will be

The wavelength of light diminishes $\mu$ times ($\mu = 1.33$ for water) in a medium. $A$ diver from inside water looks at an object whose natural colour is green. He sees the object as