A rod of length 10 cm lies along the principal axis of a concave mirror of focal length 10 cm in such a way that its enf closer to the pole is 20 cm away from the mirror. The length of the image is

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 ray of light is incident at an angle of incidence i, on one face of a prism of angle A (assumed to be small ) and emerges normally from the opposite face. If the refractive index of the prism is $$\mu $$. the angle of incidence i, is nearly equal to

A concave mirror of focal length $$f$$₁ is placed at a distance of d from a convex lens of focal length $$f$$₂. A beam of light coming from infinity and falling on this convex lens $$-$$ concave mirror combination returns to infinity. The distance d must equal