when a hollow sphere with a small hoe is immersed in water, initially a bubble of radius equal to the hole radius
is formed as shown in figure. When the bubble breaks, then water enters into the hollow sphere.
excess pressure ΔP inside the bubble is given by, ΔP = ρgh = 4T/r ......(1)
where ρ is density of water, g is acceleration due to gravity, h is height of water column above the hole of sphere,
T is surface tension and r is hole radius
hence we get, r = 4T / ( ρgh ) = ( 4×0.07) / ( 1000 × 9.8 × 40 × 10-2 ) = 7.143 × 10-5 m
diameter of hole = 2 × 7.143 × 10-5 m = 14.286 × 10-5 m = 0.143 mm