Q 12-01-067JEE MainJEE Main 2023 (29 Jan, Shift 1)Hard
In a cuboid of dimension $2L\times2L\times L$, a charge $q$ is placed at the centre of the surface $S$ having area of $4L^2$. The flux through the opposite surface to $S$ is given by
Answer: (D) $\dfrac{q}{6\epsilon_0}$
Place a second, identical cuboid on the other side of $S$. The charge is then at the centre of a cube of side $2L$, and by symmetry each of the six faces of this cube receives $\dfrac{q}{6\epsilon_0}$.
The face opposite to $S$ is one full face of this cube, so its flux is $\dfrac{q}{6\epsilon_0}$.
Solution by Sreeraj P, M.Sc Physics