Assertion (A) > : On a wet floor of a bathroom, a small circular area around a pinch of foam appears to be dry. Reason (R) > : Soap molecules reduce surface tension and increase surface area of the thin layer of water on the wet floor.

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Q: 100 (NDA-II/2009)

Assertion (A) : On a wet floor of a bathroom, a small circular area around a pinch of foam appears to be dry.
Reason (R) : Soap molecules reduce surface tension and increase surface area of the thin layer of water on the wet floor.

question_subject: 

Science

question_exam: 

NDA-II

stats: 

0,25,5,25,4,1,0

keywords: 

{'soap molecules': [0, 0, 2, 0], 'wet floor': [0, 0, 1, 0], 'surface tension': [0, 0, 2, 3], 'surface area': [0, 2, 1, 0], 'foam': [1, 0, 1, 0], 'water': [65, 15, 80, 129], 'bathroom': [0, 0, 1, 1], 'small circular area': [0, 0, 1, 0], 'thin layer': [0, 0, 1, 2]}

Option 1 states that both the assertion (A) and the reason (R) are individually true, and that the reason is the correct explanation of the assertion.

The assertion states that on a wet floor of a bathroom, a small circular area around a pinch of foam appears to be dry. This means that when a pinch of foam is placed on a wet floor, the area immediately around the foam appears dry.

The reason given is that soap molecules reduce surface tension and increase the surface area of the thin layer of water on the wet floor. Surface tension is the force that holds the molecules of a liquid together and resists an external force. When soap is added to water, it reduces the surface tension, making the water spread out more easily. This increased surface area results in a thinner layer of water around the foam, causing it to dry more quickly.

Therefore, option 1 is correct, as both the assertion and the reason are true, and the reason correctly explains why the circular area around the foam appears dry on the wet floor.