For a normal eye, the cornea of eye provides a converging power of 40 D and the least converging power of the eye lens behinf the cornea is 20 D. Using this information, the distance between the retina and the cornea-eye lens can be estimated to be

For the angle of minimum deviation of a prism to be equal to its refracting angle, the prism must be made of a material whose refractive index.

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