A proton and an alpha particle both enter a region of uniform magnetic field, B, moving at right angles to the field B. If the radius of circular orbits for both the particles is equal and the kinetic energy acquired by proton is 1 MeV, the energy acquired by the alpha particle will be:

A 1 MeV

B 4 MeV

C 0.5 MeV

D 1.5 MeV

The answer is A.

Solution

$R = \frac{mv}{qB} = \frac{\sqrt{2mK}}{qB}$
$R_\alpha = R_p$: $\frac{2(4m_p)K_\alpha}{(2e)^2B^2} = \frac{2m_pK_p}{e^2B^2}$
$K_\alpha = K_p = 1$ MeV

Concept Radius in terms of kinetic energy

13 questions from this chapter have appeared across 10 exam years.