Q.

There is a circular tube in a vertical plane. Two liquids which do not mix and of densities d1 and d2 are filled in the tube. Each liquid subtends 90° angle at centre. Radius joining their interface makes an angle α with vertical. Ratio d1d2 is

1 1+sinα1-sinα  
2 1+cosα1-cosα  
3 1+tanα1-tanα  
4 1+sinα1-cosα  

Ans.

(3)

Pressure at interface A must be same from both the sides to be in equilibrium

∴  (Rcosα+Rsinα)d2g=(Rcosα-Rsinα)d1g

⇒d1d2=cosα+sinαcosα-sinα=1+tanα1-tanα