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

For a light ray to undergo total internal reflection, light must travel from $(i = \text{angle of incidence}, i_C = \text{critical angle})$

$A$ ray of light in a liquid of refractive index $1.4$ approaches the boundary surface between the liquid and air at an angle of incidence whose sine is $0.8$. Which of the following statements is correct about the behavior of the light?

What should be the maximum acceptance angle at the air-core interface of an optical fibre if $n_1$ and $n_2$ are the refractive indices of the core and the cladding respectively?

$A$ glass slab 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 ' $\theta$ ',then the corresponding angle of refraction 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 ..............$m^2$.