Question 20N.3.SL.TZ0.b(iii)

A spherical soap bubble is made of a thin film of soapy water. The bubble has an internal air pressure $P_{\mathrm{i}}$ and is formed in air of constant pressure $P_{\mathrm{o}}$. The theoretical prediction for the variation of $\left(P_{\text{i}}-P_{\text{o}}\right)$ is given by the equation

$(P_{\mathrm{i}}-P_{\mathrm{o}})=\frac{4\mathrm{g}}{R}$

where $\gamma$ is a constant for the thin film and $R$ is the radius of the bubble.

Data for $\left(P_{\text{i}}-P_{\text{o}}\right)$ and $R$  were collected under controlled conditions and plotted as a graph showing the variation of $\left(P_{\text{i}}-P_{\text{o}}\right)$ with $\frac{1}{R}$.