NEET UG 2011 — Optics

A conversing beam of rays is incident on a diverging lens. Having passed though the lens the rays intersect at a point $15 \mathrm{~cm}$ from the lens on the opposite side. If the lens is removed the point where the rays meets will move $5 \mathrm{~cm}$ closer to the lens. The focal length of the lens is

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

Which of the following is not due to total internal reflection?

A thin prism of angle $15^{\circ}$ 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 prism produces dispersion without deviation. The angle of the second prism should be