Consider two hollow concentric spheres `S_(1) and S_(2)` enclosing charges 2Q and 4Q respectively as shown in figure. (ii) How will the electric flux through `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

When the medium is filled up with a medium of dielectric constant `epsilon_r` then, electric field,
`E = (2Q)/(4 pi epsilon_0 epsilon_r r^(2))`
`:.` Flux through `S_(1)`
`int E cdot dS = E cdot 4 pi r^(2) = (2Q)/(4 pi epsilon_(0)epsilon_(r)r^(2)) xx 4 pi r^(2) = (2Q)/(epsilon_0 epsilon_r)`.