Question

A hemisphere of radius r a point charge Q is kept at distance y above the centre such that y is tending towards 0. electric flux through the curved surface is

Answer 1

Accorging to gauss' law flux throgh an enclosed body if Q charge is enclosed by it is given by : (Q/epsilon 0)

Here y tends to zero means the charge Q is almost at the centre itself. So if it was a sphere the total flux that would go through the curved surface area is Q/epsilon0. But since it is a hemishpere, the flux is half that of sphere case. So total flux through the curved surface is (Q/2 epsilon0.)