If two soap bubbles of equal radii r coalesce then the radius of curvature of interface between two bubbles will be

Options

A. r
B. zero
C. infinity
D. `(1)/(2r)`

Answer

C

Explanation

Excess pressure as compared to atmosphere inside A is `(4S)/(r_(1))` and B is `(4S)/(r_(2))`.

The pressure difference is,
`(4S)/(r_(1)) - (4S)/(r_(2)) = (4S)/(r') rArr r' = (r_(1)r_(2))/(r_(2) - r_(1))`
Given, `r_(1) = r_(2) = r`
`:. r' = (r^(2))/(0) = oo`