Question

find an expression for electric field strength at a distant point situated on the axis of an electric dipole

Answer 1

Hello mate here is your answer.

To calculate electric field created by a dipole on the axial line ( on the same line joining the two charges),

All the measurement of distances are to be taken from the centre(O).

Let the distance between O to +q and  O to –q be ‘l’. So, total length between +q and –q will be ‘2l’.

Take a point ‘p’ on the axial line at the distance ‘r’ from the centre as shown in figure.

Hope it helps you.