Q. A proton of energy $8\ eV$ is moving in a circular path in a uniform magnetic field. The energy of an alpha particle moving in the same magnetic field and along the same path will be

A) 4 $eV$
B) 2 $eV$
C) 8 $eV$
D) 6 $eV$
Explanation

(c) $r = \frac{\sqrt{2mK}}{qB} \Rightarrow q \propto \sqrt{mK}\ \Rightarrow K \propto \frac{q^{2}}{m}$
$\Rightarrow \frac{K_{\alpha}}{K_{p}} = \left( \frac{q_{\alpha}}{q_{p}} \right)^{2} \times \frac{m_{p}}{m_{\alpha}} \Rightarrow \frac{K_{\alpha}}{8} = \left( \frac{2q_{p}}{q_{p}} \right)^{2} \times \frac{m_{p}}{4m_{p}} = 1$
$\Rightarrow K_{\alpha} = 8\ eV$

Dr. Abubacker
Reviewed by Dr. Abubacker

Physics Educator & NEET/JEE Specialist

Ph.D. in Physics with 19+ years of teaching experience.