Question

A soap bubble with a radius '$r$' is placed on another bubble with a radius $R$ (figure). Angles between the films at the points of contact will be-

• A. ${120}^o$
• B. ${30}^o$
• C. ${45}^o$
• D. ${90}^o$

Answer 1

The correct option is A ${120}^o$

Angle of contact b/w two films of soap bubble is formed by tangents of two surfaces at point of contact. Which is found to be a constant of ${120}^0$.