Write the sources of microwaves and infrared waves and their uses.

(A) Microwaves are produced by special types of vacuum tubes like Klystron,magnetron,or Gunn diodes.
They are radio waves of very short wavelength,and their frequency range varies from $0.3 \text{ GHz}$ to $300 \text{ GHz}$.
Uses of Microwaves:
$(i)$ They are used in radar systems for aircraft navigation.
$(ii)$ They are used for the control of fighter planes,naval operations,and satellite communication.
$(iii)$ Radar provides the basis for speed guns used to measure the speed of balls (tennis and cricket) and vehicles.
$(iv)$ They are used in microwave ovens. In such ovens,the frequency of the microwave resonates with the frequency of water molecules. Hence,the energy of the wave is transferred as kinetic energy to water molecules,heating the food. Domestic microwave ovens typically use $0.915 \text{ GHz}$ or $2.45 \text{ GHz}$.
Infrared waves are produced by hot bodies and their molecules. They lie between the microwave and visible regions of the electromagnetic spectrum. $LED$s can also produce infrared waves. These are often called heat waves because they are readily absorbed by water molecules,$CO_2$,and $NH_3$ present in matter. By absorbing these waves,the kinetic energy of molecules increases,causing them to heat up.
Uses of Infrared Waves:
$(i)$ Infrared bulbs are used in physical therapy.
$(ii)$ They maintain the average temperature of the Earth through the greenhouse effect.
$(iii)$ Infrared sensors are used for military purposes and monitoring crop growth in agriculture.
$(iv)$ $LED$s are used in remote controls for $TV$s,video recorders,and $Hi-Fi$ systems.