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?

Colours of thin soap bubbles are due to :s

Pick out the longest wavelength from the following types of radiations.

If two mirrors are kept inclined at 60° to each other and a body is placed at the middle, then total number of images formed is :

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 :

Rainbows are formed by

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

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 :

Interference is possible in