If f_v and f_n are the focal lengths of a convex lens for violet ad red light respectively and F_V and F_R are the focal lengths of concave lens for violet and red light respectively, then we have :

The angular resolution of a 10 cm diameter telescope at a wavelength of 5000 Å is of the order of :

A man is 6 ft tall. In order to see his entire image, he requires a plane mirror of minimum length equal to :

For the given incident ray as shown in figure, the condition of total internal reflection of the ray will be satisfied if the refractive index of block will be:

Focal length of a convex lens of refractive index 1.5 is 2 cm. Focal length of lens when immersed in a liquid of refractive index of 1.25 will be :

A telescope has an objective lens of 10cm diameter and is situated at a distance of one kilometre from two objects. Find out the minimum distance between these two objects, which can be resolved by the telescope, when the mean wavelength of light is 5000 Å.

A convex lens of focal length 80 cm and a concave lens of focal length 50 cm are combined together. What will be their resulting power?

One face of a rectangular glass plate 6 cm thick is silvered. An object held 8 cm in front of the first face, forms an image 12 cm behind the silvered face. The refractive index of the glass is :

The hypermetropia is a