An `alpha` particle 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 times at which A records zero magnetic field is `t_(1)`, 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

(b) Point A shall record zero magnetic field when the `alpha`-particle
is at positions P and Q as shown if Fig. The time taken
by `alpha`-particle to go from P to Q is

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