Q 11-09-121JEE MainJEE Main 2021 (26 Aug, Shift 1)Easy
A soap bubble of radius $3$ cm is formed inside another soap bubble of radius $6$ cm. The radius of an equivalent soap bubble that has the same excess pressure as inside the smaller bubble with respect to the atmospheric pressure is ______ cm.
Numerical value type. Enter your answer.
Answer: 2
Excess pressure inside the inner bubble relative to the atmosphere:
$$\Delta P = \frac{4T}{3} + \frac{4T}{6} = \frac{4T}{2}$$
A single bubble with this excess pressure has $\dfrac{4T}{r} = \dfrac{4T}{2}$, so $r = 2$ cm.
Solution by Sreeraj P, M.Sc Physics