$A$ right-angled glass prism is shown in the figure. $A$ liquid film is in contact with the hypotenuse face. $A$ ray of light incident normally on the face $AB$ will undergo total internal reflection from the hypotenuse face,if the refractive index of the liquid is $\mu_l$ (given $\mu_{\text{glass}} = 3/2$).

$A$ glass prism whose cross-section is an isosceles triangle stands with its (horizontal) base in water; the angles that its two equal sides make with the base are each $\theta$. An incident ray of light,above and parallel to the water surface,is totally internally reflected at the glass-water interface and subsequently re-emerges into the air. Take the refractive indices of glass and water to be $\frac{3}{2}$ and $\frac{4}{3}$,respectively. The maximum value of $\cos\theta$ is:

$A$ girl looks through a circular glass slab (refractive index $1.5$) of thickness $20 \,mm$ and diameter $60 \,cm$ to the bottom of a swimming pool. The refractive index of water is $1.33$ (or $4/3$). The bottom surface of the slab is in contact with the water surface. The depth of the swimming pool is $6 \,m$. The area of the bottom of the swimming pool that can be seen through the slab is approximately ..............$m^2$.

An optical fiber works on the principle of ......

The speed of light in media $A$ and $B$ are $2.0 \times 10^{10} \, cm/s$ and $1.5 \times 10^{10} \, cm/s$ respectively. $A$ ray of light enters from medium $B$ to $A$ at an incident angle $\theta$. If the ray suffers total internal reflection,then:

$A$ ray of light enters from a rarer to a denser medium. The angle of incidence is $i$. Then the reflected and refracted rays are mutually perpendicular to each other. The critical angle for the pair of media is