An air bubble of radius R is located at depth h below the free surface of water. Atmospheric pressure is P₀, water density is ρ and surface tension is S. What is the pressure inside the bubble?
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Question

An air bubble of radius R is located at depth h below the free surface of water. Atmospheric pressure is P₀, water density is ρ and surface tension is S. What is the pressure inside the bubble?

G1 Physics · Accepted Answer

The pressure in the surrounding water at depth h is P(out) = P₀+ρgh. An air bubble in water has one curved liquid-gas interface. Therefore its excess internal pressure is P(in)−P(out) = 2S/R. Hence, P(in) = P₀+ρgh+2S/R. Correct option: B.