The condition under which a microwave oven heats up a food item containing water molecules most efficiently is(a) the frequency of the microwaves has no relation with natural frequency of water molecules.(b) microwaves are heat waves, so always produce heating.(c) infra-red waves produce heating in a microwave oven.(d) the frequency of the microwaves must match the resonant frequency of the water molecules.
Answers
The correct answer is (d) the frequency of the microwaves must match the resonance frequency of the water molecules.
Microwaves function by exposing the food to electromagnetic radiation which belongs to the range of microwave frequency.
It causes induction of the polar molecules inside , thereby resulting in production of thermal energy by the process of dielectric heating.
As, microwaves are electromagnetic waves where frequency is in the range of 10^9 Hz to 3 * 10^11 Hz . The wavelength is in range of 1 mm to 0.3 mm .
Microwave heats up the food particles very efficiently and quickly because they passes heat energy directly to the small food molecules .
When the resonance condition occurs in microwave oven, means when frequency of microwave and frequency of water molecules are same, energy is transferred to water molecules in form of kinetic energy due to the vibrations . This cause the water molecules to vibrate, so the heat is produced.
Hence, the correct option is (d) the frequency of the microwaves must match the resonant frequency of the water molecules.