Two separate air bubbles (radii `0.002 cm` and `0.004`) formed of the same liquid (surface tension `0.07 N//m`) come together to form a double bubble. Find the radius and the sense of curvature of the internal film surface common to both the bubbles.

Explanation

`r=(r_(1)r_(2))/(r_(2)-r_(1))`
`r=(0.002xx0.004)/(0.004-0.002)=0.004`m
As the excess pr. Is always towards concave surface & pressure in smaller bubble is greater that larger bubble the common surface is concave towards the centre of the smaller bubble.