# Pressure inside a bubble of water

Would the pressure on the inside of a bubble of water be the same as that on the inside of a drop of water of the same diameter and at the same temperature?

In the case of a drop of water, the pressure inside the drop must be the same as the atmospheric pressure. In the case of a bubble, the pressure inside the bubble must be the same as that of the liquid in which it is immersed (and if the liquid is in the atmosphere, atmospheric pressure will also contribute to the total pressure inside the liquid).

For example, if you consider a bubble 50m below water, the total pressure around the bubble will be $$1$$atm from the atmosphere added to $$5\times 1$$atm from the water column above it. So the total pressure inside the bubble will be $$6$$atm. See the comment by Gert below to get more details about how to compute the water pressure based on depth.

• The submersed pressure only increases $1\mathrm{atm}$ for every $10\mathrm{m}$ of depth: $P=\rho g h=1000\mathrm{kgm^{-3}}\times 9.81\mathrm{ms^{-2}}\times 10\mathrm{m}\approx 1\mathrm{atm}$ So your pressure will be $1.5\mathrm{atm}$, not $6$
– Gert
Commented Aug 8, 2021 at 19:28
• Thanks for that! I had a typo on the first $5$m. Should have been $50$m. Already fixed, it!
– Rick
Commented Aug 8, 2021 at 19:51
• Ok, thanks for correcting that.
– Gert
Commented Aug 8, 2021 at 20:24
• But wouldn't surface tension add pressure to the pressure from outside? The pressure inside the drop should be $2\sigma /r$ compared to the pressure outside. Commented Aug 8, 2021 at 20:25
• @tomtom1-4 The answer ignores the Laplace pressure, but this is the same between an air drop in water and a water drop in air, all else equal. Commented Aug 8, 2021 at 21:40