A plane mirror $PQ$ is held normally to water surface of refractive index $1.33$. A ray of light is incident at an angle of $50°$ with the mirror surface. After reflection, the ray is refracted into water. The angle of refraction $r$ is, here $\sin 50°=0.760$.

When a ray of light is incident normally on a surface, then,

A ray of light is incident on the surface of separation of a medium with the velocity of light at an angle $45°$ and is refracted in the medium at an angle $30°$. What will be the velocity of light in the medium?

A light wave enters from air into a medium of refractive index $\frac{4}{3}$. If wavelength of light in air is $6000 \mathrm{\AA }$, then the wave number of light in medium is,

The angle of incidence is found to be twice the angle of refraction when a ray of light passes from vacuum into a medium of R.I. $\mu$. The angle of incidence will be