The workdone in increasing the size of a soap film from `10 cm xx 6 cm` to `10 cm xx 11 cm` is `3 xx 10^(-4)J.` The surface tension of the film is

Options

A. `5xx10^(-2)N//m`
B. `3xx10^(-2)N//m`
C. `1.5xx10^(-2)N//m`
D. `1.2xx10^(-2)N//m`

Answer

B

Explanation

Surface tension, `S = ("work done")/("increase in area")`
As the soap film has two surfaces.
`S =(3.0xx10^(-4)J)/(2xx(10xx11-10xx6)xx10^(-4)m^(2))`
`=3xx10^(-2) N//m`.