The critical angle for a denser-rarer interface is $45^{\circ}$. The speed of light in the rarer medium is $3 \times 10^8 \, m/s$. The speed of light in the denser medium is:

Assertion: The refractive index of diamond is $\sqrt{6}$ and that of liquid is $\sqrt{3}$. If the light travels from diamond to the liquid,it will be totally internally reflected when the angle of incidence is $30^{\circ}$.
Reason: $\mu = \frac{1}{\sin C}$,where $\mu$ is the refractive index of diamond with respect to the liquid.

The critical angle for diamond (refractive index $= 2$) is........$^o$

The phenomenon utilised in an optical fibre is

$A$ ray of light incident parallel to the base $PQ$ of an isosceles right-angled triangular prism $PQR$ suffers two successive total internal reflections at the faces $PQ$ and $QR$ before emerging reversed in direction as shown below. If the refractive index of the material of the prism is $\mu$,then

If the critical angle for total internal reflection from a medium to vacuum is $45^{\circ}$,then the velocity of light in the medium is,