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

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

(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.

A transformer is used to change a high alternating e.m.f. to a low alternating e.m.f. of the same frequency.

(a) Identify the type of transformer used for the above purpose.

(b) State whether the turns ratio of the above transformer is = 1 or >1 or <1.

A solid of mass 60 g at 100°C is placed in 150 g of water at 20°C. The final steady temperature is 25°C. Calculate the heat capacity of solid?

[sp. heat capacity of water = 4.2 J g^-1 K^-1 ]