Two short magnets of equal dipole moments `M` are fastened perpendicularly at their centres (figure). The magnitude of the magnetic field at a distance `d` from the centre on the bisector of the right angle is

Options

A. `(mu_0)/(4pi)(2Msqrt2)/(d^3)`
B. `(mu_0)/(4pi)(M)/(d^3)`
C. `(mu_0)/(4pi)(Msqrt2)/(d^3)`
D. `(mu_0)/(4pi)(2M)/(d^3)`

Explanation

Net magnetic moment of the couple of magnets is `sqrt(M^2+M^2)=Msqrt2` at `45^@` (midway). Point P lies an axial line of net magnetic moment.
Therefore, `B=(mu_0)/(4pi)(2Msqrt2)/(d^3)`