Home / Topics / AC Circuits & EM Waves
Microwaves
Beginner
Used in radar and ovens.
Wavelengths of 1 mm to 1 m; used for radar, satellite links and ovens (2.45 GHz excites water molecules).
Cosmic microwave background peaks at 160 GHz.
The oven's door mesh blocks microwaves.
In more detail
Microwaves have wavelengths from about 1 mm to 30 cm and are used in communications, radar and cooking. They are absorbed strongly by water molecules.
Real-world uses
- Microwave ovens heat food by making water molecules rotate.
- Satellite and radar communications use microwaves.
- Weather radar and microwave ovens use microwaves, which are absorbed by water and reflected by metal.
Open the interactive lesson, with simulation and quiz →
Frequently asked questions
Why do microwaves heat food?
The oscillating field makes polar molecules rotate, and friction heats the food.
Are microwaves harmful?
Not at the power levels used by ovens, which are enclosed to contain radiation.
Why do microwave ovens use metal mesh doors?
The mesh is small compared with the microwave wavelength, so it reflects the waves and keeps them inside.
Related topics in AC Circuits & EM Waves
Radiation pressure · EM spectrum · Radio waves · Infrared · Visible light · Ultraviolet