The magnetic field of a point charge is given by

Recall the Biot-Savart law for the magnetic field B created by a moving point charge:

B = μ₀/4π * qv×r/|r|³

μ₀ is the vacuum permeability (4π×10⁻7 H/m), q is the charge, v is the velocity vector, r is the position vector from the point charge to the point in space where you are measuring the B field, and |r| is the magnitude of the position vector.

d

explanation:

v=uf/(u-f)

= 5.10/(5-10) convex lens has positive focal length

=50/-5

=-10 cm (formed at other side)