Question

While snorkeling, you see air bubbles leaving a crevice at the bottom of a reef. One of the bubbles has a radius of 0.065 m. As the bubble rises, the pressure inside it decreases by 50%. Now what is the bubble's radius?

Answer 1

Pressure inside a bubble is given

P=4 $\sigma$ /r

where $\sigma$ is the surface tension of the bubble and r is radius .

so

P=4 $\sigma$ /(0.065) ----------------------------------------------------------------------(1)

now the pressure is redued to half.

P/2=4 $\sigma$ /r --------------------------------------------------------------------------(2)

dividing eq.1 by eq.2

2=r/(0.065)

r=0.13 m ANS