A particle of mass m and charge q is accelerated in a cyclotron. For a circular path of radius r1, its velocity is v1, the time period of the revolution T1. For another circular path of radius r2, its velocity is v2, the time period of the revolution T2. Then the ratio of T1 and T2 is
1
1
2
v1 : v2
3
r1 : r2
4
v1r1 : v2r2