Step 1: Place microwaves in the spectrum.
Microwaves sit between radio waves and infrared radiation, with wavelengths of the order of a centimetre. This short wavelength is the reason for most of their applications.
Step 2: List applications with the reason for each.
• RADAR and navigation: being short-wavelength and sharply beamable, they reflect off distant objects, letting us locate aircraft, ships and measure vehicle speeds.
• Cooking (microwave ovens): the microwave frequency matches the rotational response of water molecules, so energy is absorbed and food heats from within.
• Communication: satellite links, mobile/cellular networks and point-to-point microwave relays use them to carry large amounts of information.
• Analysis of molecular structure (microwave spectroscopy) is a further scientific use.
\[\boxed{\text{Radar, cooking ovens, satellite and mobile communication}}\]