When one end of the capillary is dipped in water, the height of water column is ' h '. The upward force of 108 dyne due to surface tension is balanced by the force due to the weight of water column. The inner circumference of the capillary is (surface tension of water =7 2 10⁻² ~N / m )

Step-by-step solution

Upward force due to surface tension equals the product of surface tension and inner circumference: F_T = T L . Given F_T = 108 dyne and T = 7.2 10⁻² N/m , convert F_T to newtons: 108 dyne = 108 10⁻⁵ N . Solving for circumference: L = F_T T = 108 10⁻⁵ 7.2 10⁻² . Simplifying: L = 108 7.2 10⁻³ = 15 10⁻³ m . Convert to centimeters: 15 10⁻³ 100 = 1.5 cm . The inner circumference is D .