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

Options

A. 0
B. 2r
C. `r/2`
D. infinity

Answer

D

Explanation

For two soap bubbles of radii `r_(1) and r_(2), " where " r_(2) gt r_(1)` , the rdius of curvature of the common interface is given by
` R = (r_(1)r_(2))/(r_(2)-r_(1)) `
But in this case , ` r_(1) = r_(2) " " :. R_(2) -r_(1) = 0 `
` R =(r_(1)r_(2))/0 = oo`