What form of electromagnetic radiation is used in microwave ovens to heat food?

• A. Infrared
• B. Visible light
• C. Ultraviolet
• D. Microwave

Answer: (D)

Microwave heating works because microwaves couple to polar molecules, especially water, inside the food. The alternating electric field of the microwaves makes these molecules rotate rapidly, and that molecular motion turns into heat. This converts the microwave energy directly into thermal energy throughout the food, not just on the surface. Infrared would heat mainly the outer layer, visible light isn’t efficient at heating, and ultraviolet is hazardous and not used for cooking. The oven’s metal interior reflects the microwaves to contain them and help distribute the energy.