A proton, a deuteron and an `alpha`- particle having the same kinetic energy are moving in circular trajectors in a constant magnetic field. If `r_p, r_d` and `r_(alpha)` denote respectively the radii of the trajectories of these particles then

Options

A. `r_(alpha) = r_(p) lt r_(d)`
B. `r_(alpha) gt r_(d) gt r_(p)`
C. `r_(alpha) = r_(d) lt r_(p)`
D. `r_(p) = r_(d) = r_(alpha)`

Answer

A

Explanation

`r = sqrt(2mK)/(Bq), r_(p) prop (sqrt(m))/(e), r_(d) prop (sqrt(2m))/(e), r_(alpha) prop (sqrt(4m))/(2e)`
`r_(p) = r_(alpha) lt r_(d)`