Calculate the work done against surface tension in blowing a soap bubble from a radius of `10 cm` to `20 cm`, if the surface tension of soap solution is `25xx10^(-3)N//m`.

Explanation

(i). For soap bubble: Extension in area `=2xx4pir_(2)^(2)-2xx4pir_(1)^(2)=8pi[(0.2)^(2)-(0.1)^(2)]=0.24pim^(2)`
Work done `W_(1)=` Surface tension `xx` extension in area `=25xx10^(-3)xx0.24pi=6pixx10^(-3)J`
(ii). For liquid Drop: In case of liquid drop only one free surface, so extension in area will be half of soap bubble
`thereforeW_(2)=(W_(1))/(2)=3pixx10^(-3)J`