Question

A square frame of each side \( L \) is dipped in a soap solution and taken out. The force acting on the film formed is \( T = \) surface tension of soap solution

• A. \( 2 \, T L \)
• B. \( 8 \, T L \)
• C. \( 12 \, T L \)
• D. \( R = (R_1^3 + R_2^3)^{\frac{1}{3}} \)

Hint:

The force due to surface tension on a closed surface (like a soap film on a frame) is given by \( 2n \times T \times L \), where \( n \) is the number of sides and \( L \) is the length of each side.

Answer 1

The Correct Option is B

Step 1: Surface tension on a square frame.
When a square frame is dipped in a soap solution, the soap film creates a force due to surface tension along each side of the square. The force on each side is \( T L \), and there are four sides. However, since there are two surfaces formed (front and back), the total force is: \[ F = 2 \times 4 \times T L = 8 T L \]
Step 2: Conclusion.
Thus, the force acting on the film formed is \( 8 T L \), so the correct answer is (B).