Question

A spherical soap bubble of radius $1cm$ is formed inside another soap bubble of radius $3cm$. The radius of a single soap bubble which maintains the same pressure difference as inside the smaller and outside the larger soap bubble as

• A. $0.75cm$
• B. $0.75m$
• C. $7.5cm$
• D. $7.5m$

Answer 1

The correct option is A $0.75cm$

Excess pressure inside a soap bubble $=\frac{4T}{r}$

where $r$ is the radius of the bubble.

Hence

$\frac{4T}{3}+\frac{4T}{1}=\frac{4T}{R}$

$\Rightarrow \frac{3\times 1}{3+1}cm$

​

$\Rightarrow R=0.75cm$