(a) Name the waves used for echo depth sounding.

(b) Give one reason for their use in the above application

Two bodies A and B have same kinetic energies. Compare their velocities if mass of A is four times the mass of B.

Draw a graph of potential energy vs height from the ground for a body thrown vertically upwards.

(a) Refer to the diagram given below. A lens with two different refractive indices is shown. If the rays are coming from a distant object, then how many images will be seen?

(b) A glass lens always forms a virtual, erect and diminished image of an object kept in front of it. Identify the lens.