If radius of circular paths followed by one proton and one `alpha`-particle, in the plane, perpendicular to uniform magnetic field, are equal then ratio of their momenta is _____ .

Options

A. `1:1`
B. `2:1`
C. `1:2`
D. `1:4`

Answer

C

Explanation

Equal radius of circular parth,
`r=(mv)/(Bq)=p/(Bq)`
`therefore` In p = Bqr, B and r same
`thereforeppropq`
`thereforep_(p)/p_(alpha)=q_(p)/q_(alpha)=e/(2e)=1/2`
`thereforep_(p):p_(alpha)=1:2`