Which of the following particles will describe the smallest circle when projected with the same velocity perpendicular to a magnetic field?

Options

A. electron
B. proton
C. `He^(+)`
D. `Li^(++)`

Answer

A

Explanation

`R = (mv)/(Bq), R prop (m)/(q)`
electron: `(m_(e))/(e)`, proton: `(m_(p))/(e), He^(+): (3m_(p))/(2e) = (2m_(p))/(e)`
`Li^(++): (7m_(p))/(2e) = 3.5 (m_(p))/(e)`
`(m_(e))/(e)` is minimum