Consider two hollow concentric spheres `S_(1)` and `S_(2)` enclosing charges 2Q and 4Q respectively, as shown in the figure.
How will the electric flux through the sphere `S_(1)` change if a medium of dielectric constant `epsilon_(r)` is introduced in the space inside `S_(1)` in place of air ? Deduce the necessary expression.

Explanation

If a medium of dielectric constant `epsilon_(r)` is introduced in the space inside `S_(1)` in place of air, then
`phi_(S_(1))=(Sigmaq)/(epsilon_(0)epsilon_(r))=(2Q)/(epsilon_(0)epsilon_(r))`