A convex lens of radii of curvature 6 cm and 12 cm is immersed in a liquid of refractive index 1.3. If the refractive index of the material of the lens is 1.5 , then the focal length of the lens when immersed in the liquid is

When unpolarised light from air incidents on the surface of a medium of refractive index $\sqrt{3}$, then the reflected light is totally polarised. The angle of refraction is

An object of height 3.6 cm is placed normally on the principal axis of a concave mirror of radius of curvature 30 cm . If the object is at a distance of 10 cm from the principal focus of the mirror, then the height of the real image formed due to the mirror is

Monochromatic light of wavelength $6000 \mathop {\rm{A}}\limits^{\rm{o}} $ incidents on a small angled prism. If the angle of the prism is $6^{\circ}$, the refractive indices of the material of the prism for violet and red lights are respectively 1.52 and 1.48 , then the angle of dispersion produced for this incident light is