Kinetic energy of electron,

∴ speed of electron,

Since the velocity (Vector v) of the electron makes an angle of *θ* = 60º with the magnetic field Vector B, the path will be a helix. So, the particle will hit S if

GS = nP Here n = 1, 2, 3, .........

But for B to be minimum, n = 1

Substituting the values, we have