When two soap bubbles stay in contact, what is the radius of the 'interface?

What is the angle of contact?

When an air bubble rise in water, what happens to its potential energy?

What is the length of the radius of the earth?

When two soap bubbles of radii r_1 and r_2 ( r_2>r_1 )coalese, the radius of curvature of common surface is

Give two examples of contact force.

Two lenses 3D and -1.5 D were put in contact. What is the focal length of the combination?

What is the role of Bithional in toilet soap?