A proton of mass $m$ and charge $+e$ is moving in a circular orbit in a magnetic field with energy $1\mathrm{ }\mathrm{MeV}$. What should be the energy of $\mathrm{\alpha }-\mathrm{p}\mathrm{a}\mathrm{r}\mathrm{t}\mathrm{i}\mathrm{c}\mathrm{l}\mathrm{e}$ ($mass = 4m$ and $charge = + 2e$), so that it can revolve in the path of the same radius?

• Correct answer
  A

  $1\mathrm{ }\mathrm{MeV}$
• B

  $4\mathrm{ }\mathrm{MeV}$
• C

  $2\mathrm{ }\mathrm{MeV}$
• D

  $0.5\mathrm{ }\mathrm{MeV}$

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