Total internal reflection of light is possible when light enters from

If the critical angle for total internal reflection from a medium to vacuum is $30^{\circ}$,then the velocity of light in the medium is:

The critical angle for total internal reflection of light going from medium $I$ to medium $II$ is given by the relation $\tan i_C = \frac{5}{9}$. The refractive index of medium $I$ with respect to medium $II$ is:

$A$ ray of light is incident on the hypotenuse of a right-angled prism after travelling parallel to the base inside the prism. If $\mu$ is the refractive index of the material of the prism, the maximum value of the base angle for which light is totally reflected from the hypotenuse is

Light is incident from a medium into air at two possible angles of incidence $(A) \ 20^o$ and $(B) \ 40^o$. In the medium,light travels $3.0 \ cm$ in $0.2 \ ns$. The ray will

$A$ step index fibre has a relative refractive index difference of $0.88\%$. What is the critical angle at the core-cladding interface in degrees?