Why does a microwave oven heat up a food item containing water molecules efficiently?
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → The frequency of the microwaves selected is to match the frequency of water molecules
Heating in a microwave oven is a resonance effect: water molecules absorb energy most efficiently from radiation whose frequency equals their natural (resonant) frequency, and the absorbed energy becomes kinetic energy of the molecules, that is, a rise in temperature of the food.
NCERT (2026-27):
Microwaves – “… Microwave ovens are an interesting domestic application of these waves. In such ovens, the frequency of the microwaves is selected to match the resonant frequency of water molecules so that energy from the waves is transferred efficiently to the kinetic energy of the molecules. This raises the temperature of any food containing water.”