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 when the `alpha`-particle is at position `P` and `Q` as shown in figure. The time taken by `alpha`-particle to go from `P` to `Q` is

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