$A$ ray of light is incident on a transparent sphere at an angle of $\pi / 4$ and is refracted at an angle $r$. The ray emerges from the sphere after suffering one internal reflection. The total angle of deviation of the ray is

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

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:

Immiscible transparent liquids $A, B, C, D$ and $E$ are placed in a rectangular glass container,forming layers based on their densities. The refractive indices of the liquids are given in the table below. The container is illuminated from the side,and a small piece of glass with a refractive index of $1.61$ is gently dropped into the liquid layers. In which liquid will the glass piece not be visible as it descends?
| Liquid | Refractive Index |
| :--- | :--- |
| $A$ | $1.51$ |
| $B$ | $1.53$ |
| $C$ | $1.61$ |
| $D$ | $1.52$ |
| $E$ | $1.65$ |

The distance travelled by light in glass (refractive index $= 1.5$) in a nanosecond will be.......$cm$.

What is refraction of light?