Originally Posted by **ling233** I have one more question here . I was also told that the pressure at the concave side of the bubbles is higher ... why is it so ? |

You have used the word "pressure" but I assume you mean stress. In other words you are asking why stress in the shell of a spherical pressure vessel is higher along the inside of the shell than on the outside - is that correct? As I noted earlier, for a thin shell like a bubble the stress is essentially constant across the width of the shell wall. Where did you hear that the stress in a bubble is higher on the inside than the outside?

Originally Posted by **ling233** is it because of the circumference of the pressure at the concave side is higher? |

Sorry, but I don't understand what you are trying to say here. Pressure doesn't have a circumference.

The mathematics of calculating stress in a spherical thick shell is quite complicated, and so in practice one would likely use a finite element technique to model the stress distribution. But think about how with increasing radius in the shell wall the forces that are pressing outward are distributed over a larger area of the shell, so consequently the stress (force per unit area) in the shall gest smaller. This really only applies to thick shells - for a thin shell like a bubble the stress across the width of the shell is essentially constant.