5.16 (a) Owing to surface tension, the pressure inside a bubble is higher than the outside pressure. Let this excess pressure be Ap. By equating the work done, Ap dV, due to an infinitesimal increase dr in the radius r to the increase in surface energy y dA, show that Ap=2ylr. (b) Calculate the excess pressures inside water bubbles of radius 1.0 mm and 1.0 m.