Question

Assertion (A): Microwave oven heats a food item containing water molecules most efficiently.
Reason (R): Resonant frequency of water molecules matches the frequency of microwaves generated by microwave oven.

• (A) and (R) are true and (R) is the correct explanation of (A)
• (A) and (R) are true but (R) is not the correct explanation of (A)
• (A) is true, but (R) is false
• (A) is false, (R) is true

Hint:

Microwave ovens heat polar molecules like water efficiently because the frequency of microwaves is close to the rotational resonance frequency of water, converting electromagnetic energy into thermal energy effectively.

Answer 1

The Correct Option is A

Step 1: Understand the assertion.
Microwave ovens heat food efficiently, especially those containing water, because water molecules absorb microwave energy effectively and convert it to heat.

Step 2: Identify the principle behind heating.
Microwaves interact with polar molecules like water. The oscillating electric field causes the water molecules to rotate rapidly, producing friction and heat within the food.

Step 3: Role of resonant frequency.
Water molecules have natural rotational frequencies. When the frequency of microwaves matches this resonance, energy absorption is maximized, leading to efficient heating.

Step 4: Check the reason statement.
The reason states that microwaves have a frequency close to the resonant frequency of water molecules. This is correct and explains why the heating is efficient.

Step 5: Relation between assertion and reason.
The assertion claims efficient heating; the reason explains why this efficiency occurs through resonance of water molecules with microwave frequency.

Step 6: Conclusion.
Both the assertion and the reason are true, and the reason correctly explains the assertion.