Light is incident normally on face $AB$ of a prism as shown in the figure. $A$ liquid of refractive index $\mu$ is placed on face $AC$ of the prism. The prism is made of glass of refractive index $\frac{3}{2}$. The limit of $\mu$ for which total internal reflection takes place on face $AC$ is

$A$ point source $S$ is placed at the bottom of a transparent block of height $h = 10 \ mm$ and refractive index $n_B = 2.72$. It is immersed in a liquid of lower refractive index $n_L$ as shown in the figure. It is found that the light emerging from the block into the liquid forms a circular bright spot of diameter $D = 11.54 \ mm$ on the top surface of the block. The refractive index of the liquid $n_L$ is:

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

The minimum area of the disc needed to cut off all the light coming out of water $\left(\mu_{w} = \frac{4}{3}\right)$ from a point source of light placed $7 \ m$ below the water surface is: (in $\pi \ m^2$)

Glass has a refractive index $\mu$ with respect to air,and the critical angle for a ray of light going from glass to air is $\theta$. If a ray of light is incident from air on the glass with an angle of incidence $\theta$,the corresponding angle of refraction is:

Critical angle of incidence for a pair of optical media is $45^{\circ}$. The refractive indices of the first and second media are in the ratio: