A ray of light passes from the vacuum into a medium of refractive index 'n'. If the angle of incidence is twice the angle of refraction, then the angle of incidence in terms of refractive index is

A convex lens having refractive index 1.6 has focal length 12 cm, when it is in air. The focal length of that lens when placed in water is (refractive index of water = 1.28)

A simple microscope is used to see the object first in blue light and then in red light. Due to the change from blue to red light, what is the effect on its magnifying power?

The angle of minimum deviation produced by a thin prism in air is $\delta_1$. What will be the minimum deviation ($\delta_2$) if the prism is immersed in liquid ?
$\left[ {}^a n_g = \dfrac{3}{2}, \ {}^a n_\ell = \dfrac{1}{3} \right]$