If the critical angle for total internal reflection from a medium to vacuum is $30^o$,the velocity of light in the medium is

The critical angle for diamond with respect to air is nearly (in $^{\circ}$)

If the refractive index of water is $\frac{4}{3}$ and that of a given glass slab immersed in it is $\frac{5}{3}$,the value of the critical angle for a ray of light tending to go from glass to water is:

The wavelengths of light in two liquids $x$ and $y$ are $3500 \, \mathring{A}$ and $7000 \, \mathring{A}$ respectively. The critical angle of $x$ with respect to $y$ is .......... $^o$.

$A$ ray of light passes from a medium $A$ having refractive index $1.6$ to the medium $B$ having refractive index $1.5$. The value of the critical angle of medium $A$ is . . . . . . .

$A$ right-angled isosceles prism is held on the surface of a liquid composed of miscible solvents $A$ and $B$ of refractive index $n_{A}=1.5$ and $n_{B}=1.3$,respectively. The refractive index of the prism is $n_{p}=1.5$ and that of the liquid is given by $n_{L}=C_{A} n_{A}+(1-C_{A}) n_{B}$,where $C_{A}$ is the percentage of solvent $A$ in the liquid. If $\theta_{C}$ is the critical angle at the prism-liquid interface,the plot which best represents the variation of the critical angle with the percentage of solvent is