The two soap of bubbles of equal radii (r and r) coalesce. Then what will be the radius of curvature of the interface between two bubbles?

Explanation

For two soap bubble of radii `r_1` and `r_2` where `r_2 gt r_1`, the radius of curvature of the common interface is given by
`R = (r_1r_2)/(r_2 - r_1)` But, in this case
`r_1 = r_2` therefore r_2 - r_1` = 0
R = (`r_1r_2`)/0 = 8