Two lenses L1 and L2 of powers 10 D and -(10/3) D respectively, separated by 50 cm, are arranged parallel to each other in vertical planes. An object is placed 15 cm to the left of L1, vertically on the common axis of the lenses. Find the distance between the original object and the final image.

The magnifying power of an astronomical telescope in normal adjustment is 10 and the focal length of its eyepiece is 20 cm. The focal length of its objective lens will be:

If the speed of light is 2.12 × 108 m/s inside the medium of an equilateral prism, find the angle of minimum deviation (δm). (Take speed of light in vacuum c = 3 × 108 m/s, sin 45° = 0.707)