[Physics] Bubble formation

surface-tension

I know that surface tension plays a key role in the formation of a bubble. I guess a bubble contains air inside it. Now how is it so that a soap bubble contains air both inside it and outside it?

I will be grateful to an answer donor if he explains me the various stages of bubble formation. In brief "How to make a bubble from a glass of water, what are the various processes that take place during the bubble formation"??

Best Answer

The air inside is at a slightly higher pressure than the air outside, so the surface tension times the change in surface area is equal to the difference in pressure times the change in volume under an infinitesimal defomation, by the principle of virtual work.

The processes that make a bubble are

  • monolayer formation when you extract the wand, with a thin sheet of liquid separating two soap monolayers.
  • Expansion of the monolayers when you blow on the wand, until they come close.
  • Bilayer separation and rejoining, which makes a topological change in the surface of the bubble, when the two bilayers touch.

None of these three processes have been studied in quantitative detail as far as I know.

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