Ionized hydrogen atoms and `alpha`-particles with same momenta enters perpendicular to a constant magnetic field, B. The ratio of their radii of their paths `r_(H):r_(alpha)` will be :

Options

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

Answer

B

Explanation

Here `q_(H)=eandq_(alpha)=2e`
For circular motion,
`(mv^(2))/r=Bqv`
`thereforer=(mv)/(Bq)" "(because"m,v,B are constant")`
`thereforerprop1/q`
`thereforer_(H)/r_(alpha)=q_(alpha)/q_(H)=(2e)/e=2/1`