The excess pressure inside a soap bubble of radius 8mm raises the height of an oil columns by 2mm. Find the surface tension of the soap solution. Density of the oil=0.8g. `Cm^-3`.

Explanation

Excess pressure in a soap bubble `(p)=(4T)/(r ).`
Again, `p=h rhog, h=` height of the oil column.
Now, `(4T)/(r )=h rho g or, T=(h rho g xxr)/(4)=(0.2xx0.8xx980xx0.8)/(4)`
`[because h = 2mm=0.2 cm, rho=0.8g. Cm^-3. g=980 cm. s^-2 and r=8 mm= 0.8 cm]`
`therefore T=31.36 dyn. cm^-1`.