(a) Why are infra-red waves often called heat waves ? Explain.
(b) What do you understand by the statement, ..Electromagnetic waves transport momentum.. ?

Explanation

(a) Infrared waves are produced by hot bodies and are characterised by their heating property.Therefore, infrared waves are often called heat waves.
(b) Like all travelling waves, the electromagnetic waves also transport momentum. Consider a plane perpendicular to the direction of propagation of an electromagnetic wave. If electric charges are there on this plane they will be set and sustained in motion by the electric and magnetic fields of the electromagnetic waves. The charges thus acquire energy and momentum from the waves and thus electromagnetic waves transport momentum.