Two identical charged spheres are suspended by strings of equal lengths. The strings make an angle $\theta$ with each other. When suspended in water the angle remains the same. If density of the material of the sphere is $1.5 \mathrm{~g} / \mathrm{cc}$, the dielectric constant of water will be $\underline{\hspace{2cm}}$. (Take density of water $=1 \mathrm{~g} / \mathrm{cc}$ )