An electron is moving in a circular path under the
influence of a transverse magnetic field of
3.57 ``10^{-2}`` T. If the value of e/m is
1.76 X ``10^{11}`` C/kg, the frequency of revolution of
the electron is :-
(1) 62.8 MHz
(2) 6.28 MHz
(3) 1 GHz
(4) 100 MHz