Two soap bubble of radii 3 mm and 4 mm are in contact radius of curvature of interface between those two bubbles is

Options

A. 1 mm
B. 7 mm
C. 12 mm
D. 12/7 mm

Answer

C

Explanation

` r = (r_(1)r_(2))/(r_(2)-r_(1)) = ( 3 xx 4 xx 10^(-6))/(10^(-3)(4-3))= 12` mm