Question

A proton and an alpha particle of the same velocity enter in a uniform magnetic field which is acting perpendicular to their direction of motion. The ratio of the radii of the circular paths described by the alpha particle and proton is

• A. 1:4
• B. 4:1
• C. 2:1
• D. 1:2

Answer 1

Answer: (C)

2:1

Answer 2

Radius, $R=\frac {mv}{qB}$
The ratio of the radii of the circular paths,
$\frac {R_α}{R_p}=\frac {\frac {m_α}{q_α}}{\frac {m_p}{q_q}}$

$\frac {R_α}{R_p}=\frac 21$

So, Answer is (C): $2:1$