A proton and an `alpha`-particle enter a uniform magnetic field perpendicular with the same speed. If proton takes `20mu` seconds to make 5 revolutions, then the periodic time for the `alpha`- particle would be

Options

A. `50 mu sec `
B. `25 mu sec`
C. `10 mu sec`
D. `5 mu sec`

Answer

C

Explanation

`T=(2pim)/(qB)`
`(T_(alpha))/(T_(P))=(m_(alpha))/(m_(p))xx(q_(p))/(q_(alpha))`
`T_(alpha)=4/1xx1/2 xx5xx10^(-6)=10 mu sec`