Assertion (A): Evaporation of sweat from human skin dissipates body heat. Reason (R): High humidity on a hot day increases discomfort.
- ABoth (A) and (R) are true and (R) is the correct explanation of (A)
- B(A) is true, but (R) is false
- C(A) is false, but (R) is true
- DBoth (A) and (R) are true, but (R) is not the correct explanation of (A)
Show answer and explanation
Correct answer: (d) Both (A) and (R) are true, but (R) is not the correct explanation of (A)
Explanation
(A) is true: sweat evaporating from skin absorbs the latent heat of vaporisation, cooling the body.
(R) is true: high humidity slows evaporation of sweat, reducing cooling and increasing discomfort.
Both are true, but (R) describes a hindrance to cooling and does not explain the heat-loss mechanism in (A).