Q100 / 180 · AIIMS 2010 · Physics

Assertion : If a proton and an a-particle enter a uniform magnetic field perpendicularly with the same speed, the time period of revolution of aparticle is double that of proton. Reason : In a magnetic field, the period of revolution of a charged particle is directly proportional to the mass of the particle and is inversely proportional to charge of particle.

  • Correct answer
    A
    If both assertion and reason are true and reason is the correct explanation of assertion
  • B
    If both assertion and reason are true but reason is not the correct explanation of assertion
  • C
    If assertion is true but reason is false
  • D
    If both assertion and reason are false.

Solution

The period of a charged particle in a magnetic field is given by $T=\frac{2 \pi m}{q B}$, i.e., $T \propto \frac{m}{q}$ We know that, $m_p=m, m_\alpha=4 m, q_p=e, q_\alpha=2 e$ $$ \therefore \frac{T_p}{T_\alpha}=\frac{1}{2} \text { or } T_\alpha=2 T_p $$

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

Relevant Questions