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How does a microwave oven work?
Quick answer
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.
Step by step
- A device called a magnetron generates microwaves at about 2.45 gigahertz.
- The waves make water (and fat and sugar) molecules in the food flip back and forth rapidly.
- That molecular motion is heat — friction between jiggling molecules warms the food.
- A metal mesh in the door reflects microwaves back inside so they can't escape.
- It heats watery food well but can't brown or crisp the way dry heat does.
People also ask
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.
How does a microwave heat food?
Microwaves make water molecules vibrate rapidly; that vibration generates heat throughout the food.
Why do microwaves heat unevenly?
Waves form hot and cold spots; that's why ovens have turntables and you stir food partway through.
Part of the guide: Everyday Machines →