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.
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.
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