When a charged particle moves in a magnetic field, the time it takes to make one full round (the time period) is given by:
T=Bq2πm​Here,
m is the mass of the particle,
q is its charge, and
B is the magnetic field. This means the time period depends on the ratio of mass to charge (
cn​To compare the time periods of a proton (
Tp​ ) and an alpha particle (
Tα​ ), use this ratio:
Tα​Tp​​=mα​mp​​×qp​qα​​An alpha particle has a mass four times that of a proton (
mα​=4mp​ ) and a charge twice that of a proton (
qα​=2qp​ ).
Plug these values in:
Tα​Tp​​=4mp​mp​​×qp​2qp​​=41​×2=21​This shows that the time taken by a proton is half that of the alpha particle. So, the ratio of their times is
Tp​:Tα​=1:2