Question

What are microwaves? How are they produced? Give any two uses of microwaves.

Hint:

Microwaves have a frequency of 1 GHz to 300 GHz and are made by klystron, magnetron or Gunn diode. Uses include microwave ovens and radar.

Answer 1

Step 1: What are microwaves?
Microwaves are electromagnetic waves with a short wavelength. Their frequency lies in the range of about 1 GHz to 300 GHz. Their wavelength is about 1 mm to 30 cm. They lie between radio waves and infrared waves in the electromagnetic spectrum.

Step 2: How are they produced?
Ordinary circuits cannot make such high frequencies. Microwaves are produced by special vacuum tubes such as the klystron, the magnetron and the Gunn diode.
In these devices, electrons move in a controlled way through cavities or in a magnetic field. They set up very fast oscillations of the electric and magnetic fields. These oscillations are the microwave radiation.

Step 3: Use 1 - microwave oven.
Microwaves have a frequency close to the natural frequency of water molecules. Food absorbs the waves, the water molecules vibrate and the food gets heated.

Step 4: Use 2 - radar and communication.
Their short wavelength lets them travel as narrow beams. So they are used in radar to find the position and speed of aircraft. They also carry signals in mobile phones and satellite links.

Final Answer:
Microwaves are electromagnetic waves of frequency about 1 GHz to 300 GHz, produced by klystron, magnetron or Gunn diode. Two uses are microwave ovens and radar.