Question

The length of each side of a cubical vessel is l. If charge q is placed at one of the vertices of the cube as shown in the figure , then flux passing through the shaded portion of the cube ​

Answer 1

$\frac{q}{24e}$

total flux contributed by the charge=q/8e

because the the field lines emerging from the charge are parallel to three surfaces which it touches( remember field lines are vectors which emerge in all directions possible, try to visualize 3D) the flux through these surfaces =0.

hence the flux is passing through only three faces.

therefore flux through one surface is 1/3 times q/8e=q/24e