$A$ cut diamond sparkles because of its

What is total internal reflection?

$A$ ray of light is travelling from glass to air. (refractive index of glass $= 1.5$). The angle of incidence is $50^{\circ}$. The deviation of the ray is

Consider a glass prism immersed in a liquid as shown below. The refractive index of glass and liquid is $1.5$ and $1.2$, respectively. $A$ ray of light enters the prism perpendicular to the face $AB$. If the ray is totally internally reflected at the face $AC$, then the largest value of angle $\theta$ is:

$A$ diver in a swimming pool wants to signal his distress to a person lying on the edge of the pool by flashing his waterproof flashlight. In which direction should he direct the beam?

An optical fibre consists of a core of refractive index $\mu_1$ surrounded by a cladding of refractive index $\mu_2 < \mu_1$. $A$ beam of light enters from air at an angle $\alpha$ with the axis of the fibre. The highest angle $\alpha$ for which the ray can travel through the fibre is: