Technology
How does a microwave oven work?
A microwave oven works by flooding food with microwaves — a type of electromagnetic wave — that make water molecules vibrate. That rapid jiggling is heat, so the food warms from the inside out, cooking far faster than a conventional oven.
See it in motion.
Watch a 2-minute animated lesson that shows exactly how a microwave oven works.
Step by step
- 1A device called a magnetron generates microwaves at about 2.45 gigahertz.
- 2The waves make water (and fat and sugar) molecules in the food flip back and forth rapidly.
- 3That molecular motion is heat — friction between jiggling molecules warms the food.
- 4A metal mesh in the door reflects microwaves back inside so they can't escape.
- 5It heats watery food well but can't brown or crisp the way dry heat does.
Frequently asked questions
- Why can't you put metal in a microwave?
- Metal reflects microwaves and can concentrate charge on edges, creating sparks that may damage the oven or start a fire.
- Are microwaves radioactive?
- No. Microwaves are low-energy, non-ionizing radiation — they heat water but can't alter atoms or make food radioactive.
- Why does microwaved food heat unevenly?
- The waves form hot and cold spots and penetrate only a few centimeters, so the turntable and a rest time help even it out.