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Q114
(IAS/1996)
Science & Technology › Basic Science (Physics, Chemistry, Biology) › Thermal physics
Answer Verified
When an air bubble at the bottom of a lake rises to the top, it will
Result
Your answer:
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·
Correct:
A
Explanation
An air bubble rising from the bottom to the surface experiences a decreasing hydrostatic (ambient) pressure; gases expand when the external pressure on them falls. Texts note that pressure compresses gases (higher pressure → smaller volume), so a reduction in pressure causes the gas to occupy more volume [1]. More specifically, as a parcel (or bubble) rises the ambient pressure decreases with height and its volume increases accordingly [2]. This behavior is described by Boyle’s law (PV ≈ constant for a given amount of gas at near-constant temperature), which directly explains why the bubble grows as the surrounding water pressure drops during ascent .
Sources
- [1] Science ,Class VIII . NCERT(Revised ed 2025) > Chapter 9: The Amazing World of Solutes, Solvents, and Solutions > 9.5.3 Effect of pressure on density > p. 148
- [2] Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 22: Vertical Distribution of Temperature > A Parcel of Rising Air > p. 297
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