Q90 / 90 · JEE Main 2012 (Offline) · Physics

Proton, Deuteron and alpha particle of the same kinetic energy are moving in circular trajectories in a constant magnetic field. The radii of proton, deuteron and alpha particle are respectively $r_p, r_d$ and $r_\alpha$. Which one of the following relations is correct?

  • A
    $r_\alpha=r_p=r_d$
  • Correct answer
    B
    $r_\alpha=r_p < r_d$
  • C
    $r_\alpha>r_d>r_p$
  • D
    $r_\alpha=r_d>r_p$

Solution

$r=\frac{\sqrt{2 m K}}{B q}$ $r \propto \frac{\sqrt{m}}{q}$ $r_\alpha=r_p < r_d$

Hence, the correct answer is option: 'B'.

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