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.

Options

A. 0.001 cm
B. 0.002 cm
C. 0.004 cm
D. 0.003 cm

Answer

C

Explanation

`r=(r_(1)r_(2))/(r_(2)-R_(1))`
As the excess pressure is always towards concave surface & pressure in smaller bubble is greater than larger bubble, the common surface is concave towards the centre of the small bubble.