An `alpha` is moving along a circle of radius R with a constant angular velocity `omega`. Point A lies in the same plane at a distance 2R from the centre. Point A records magnetic field produced by the `alpha`-particle. If the minimum time interval between two successive time at which A records zero magnetic field is t, the angular speed `omega`, in terms of t, is

Options

A. `(2pi)/(t)`
B. `(2pi)/(3t)`
C. `(pi)/(3t)`
D. `(pi)/(t)`

Answer

B

Explanation

Point A shall record zero magnetic field (due to `alpha-` particle) when the `alpha-` particle is at position P and Q as shwon in figure. The time taken by `alpha-`particle to go from P to Q is

`t=(1)/(3)(2pi)/(omega)` or `omega=(2pi)/(3t)`