A microwave oven heats food primarily by exciting which specific molecules in the food? MCQ with Answer and Explanation

A microwave oven heats food primarily by exciting which specific molecules in the food?
A. Water molecules
B. Fat molecules
C. Carbohydrate molecules
D. Protein molecules
Answer: Option A
Solution (By JKExamLibrary)
Microwave ovens use electromagnetic radiation in the microwave frequency range (usually around 2.45 GHz). Water molecules have a permanent electric dipole moment. The oscillating electric field of the microwaves rapidly forces the water molecules to flip back and forth to align with the field, generating thermal energy via friction and effectively heating the food from within.

This question belongs to: Science Physics

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Question #1 Report Error
Two waves interfering at a point have a path difference of lambda / 2. Their corresponding phase difference is exactly:
A. pi radians
B. 2pi radians
C. pi / 4 radians
D. pi / 2 radians

Correct Answer: Option A


Explanation:
The relationship between phase difference (phi) and path difference (delta x) is given by the formula phi = (2pi / lambda) * delta x. Given a path difference of lambda / 2, substitute this into the formula: phi = (2pi / lambda) * (lambda / 2) = pi radians. This indicates strictly destructive interference.

This question belongs to: Science Physics
Question #2 Report Error
The instrument used to measure intensity of earthquakes is
A. Seismograph
B. Hygrometer
C. Richter scale
D. Barometer

Correct Answer: Option A


Explanation:
Seismograph records seismic waves. Richter scale quantifies magnitude.

This question belongs to: Science Physics
Question #3 Report Error
Which of the following is a renewable source of energy?
A. Nuclear fuel
B. Petroleum
C. Coal
D. Solar energy

Correct Answer: Option D


Explanation:
Solar, wind, hydro, biomass renewable. Coal, oil, natural gas fossil fuels, non-renewable. Nuclear fuel uranium finite. Renewable replenish naturally.

This question belongs to: Science Physics