The focal length of a concave mirror with a radius of curvature of 20.0 cm is :

A. Latent heat B. Nuclear fusion C. Refractive index D. Stock value

A. Collision between fast neutrons and nitrogen nuclei present in the atmosphere. B. Action of ultraviolet light from the sun on atmospheric oxygen. C. Action of solar radiations particularly cosmic rays on carbon dioxide present in the atmosphere. D. Lightning discharge in atmosphere.

A. Work done in rolling is more than in lifting. B. Work done in lifting the stone is equal to rolling it. C. Work done in both is same but the rate of doing work is less in rolling. D. Work done in rolling a stone is less than in lifting it.

A. Viscosity of ink B. Capillary action phenomenon C. Diffusion of ink through the blotting D. Siphon action