Two identical charged sphere are suspended by strings of equal length. The strings make an angle of `30^@` with each other. When suspended in liqquid of density 0.8 g/c, the angle remain the same. The dielectric constant of the liquid is [density of the material of sphere is 1.6 g/cc]

Explanation

When set up shown in figure is in air, we have `tan 15^(@)=F/(mg)` When set up is immersed in the medium as shown in figure, the electric force experienced by the ball will reduce and will be equal to `F/epsilon_(r)` and the effective graviational force will become `mg(1-rho_(l)/rho_(s))`
Thus we have `tan 15^(@)=(F)/(mg in_(r)(1-rho_(l)/rho_(s)))=(F)/(mg) rArr in_(r)=1/(1-rho_(l)/rho_(s))=2`