The Pressure Excess Notion: Why is the Formula Multiplied by 2?

[kthouz]

in the surface tension about the pressure excess notion i have problem: why for a full dropplet of water the formula is p=2T/r whereas for a bubble p=4T/r. Why does it be multiplied by 2.

 

[lpfr]

In a filled drop there is only a surface. In a bubble there is also the internal surface. When you increase the radius, in the first cas,e only a surface increases. In the second, two surfaces increase.