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:

In an optical fibre,the refractive index of the inner part (core) is $1.68$ and the refractive index of the outer part (cladding) is $1.44$. The numerical aperture of the fibre is ........

$A$ 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:

$A$ glass prism $(\mu = 1.5)$ is dipped in water $(_a\mu_w = 4/3)$ as shown in the figure. $A$ light ray is incident normally on the surface $AB$. It reaches the surface $BC$ after being totally internally reflected at the surface $AC$,if:

Why is mirage formation seen in deserts during the summer?

$A$ beam of light consisting of red,green,and blue colors is incident on a right-angled prism as shown. The refractive indices of the material of the prism for red,green,and blue wavelengths are $1.39, 1.44$,and $1.47$ respectively. The prism will: