Physics Questions

The lens which have atleast one inward curved surface is a concave lens. Concave ens is a diverging lens as it spreads out light rays that have been refracted through it.

A concave lens is thinner at its centre than at its edges.

Resistances of both the bulbs are

R1=V^2/P1 = 220^2/25

R2 = V^2/P2 = 220^2/100

Hence  R1gt ; R2

When connected in series, the voltages divide in them in the ratio of their resistances. The voltage of 440 V devides in such a way that voltage across 25 w bulb will be more than 220 V. Hence 25 w bulb will fuse.

The metal ball can be considered  to be made up of several layers of thinner ones. On heating each of these layers will increase in radius. As the inner most layer also increases its radius, the volume inside it i.e, the volume of the hollow portion will also increase.

It is the friction between the feet and the ground that helps us to walk. Without this friction we would slip and fall

The Surface tension pulls the surface of the drop equally at all points thus produces the spherical shape having the minimum surface area. This surface tension is the "skin" of a body of water that makes the molecules stick together.