Proton and `alpha`-particle projected perpendicularly in a magnetic field, if both move in a circular path with same speed. Then ratio of their radii is

Options

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

Answer

A

Explanation

When a charged particles of charge of q is projected perpendicularly in a uniforme magnetic field B, it follow a circular path of radius R,`R=(mv)/(qB)`
Since v andB are the same fo the given two particles `Rprop(m)/(q)`
`(R_(p))/(R_(alpha))=(m_(p))/(q_(p))xx(q_(alpha))/(m_(alpha))=(m)/(e)xx(2e)/(4m)=(1)/(2)`