If the critical angle for a material to air is $30^o$,the refractive index of the material will be

The critical angle for light going from medium $A$ into medium $B$ is $\theta$. The speed of light in medium $A$ is $V_A$. What is the speed of light in medium $B$?

$A$ ray of light travelling in a transparent medium of refractive index $\mu$ falls on a surface separating the medium from air at an angle of incidence of $45^o$. For which of the following values of $\mu$ can the ray undergo total internal reflection?

$A$ green light is incident from the water to the air-water interface at the critical angle $(\theta)$. Select the correct statement.

If light travels a distance $x$ in time $t_1$ sec in air and $10x$ distance in time $t_2$ sec in a certain medium,then find the critical angle of the medium.

Explain the principle,construction,and working of an optical fibre.