When a biconvex lens of glass having refractive index 1.47 is dipped in a liquid, it acts as a plane sheet of glass. This implies that the liquid must have refractive index

A converging beam of rays is incident on a diverging lens. Having passed through the lens the rays intersect at a point 15 cm from the lens on the opposite side. If the lens is removed the point where the rays meet will move 5 cm closer to the lens. The focal length of the lens is

A thin prism of angle 15^o made of glass of refractive index $$\mu $$₁ = 1.5 is combined with another prism of glass of refractive index $$\mu $$₂ = 1.75. The combination of the prisms produces dispersion without deviation. The angle of the second prism should be

A biconvex lens has a radius of curvature of magnitude 20 cm. Which one of the following options describe best the image formed of an object of height 2 cm placed 30 cm from the lens ?