Question

A proton and an alpha particle enter into a uniform magnetic field with the same velocity.The period of rotation of the alpha particle will be

• A. four times that of proton
• B. two times that of proton
• C. three times that of proton
• D. same as that of proton

Answer 1

Answer: (B)

two times that of proton

$T=\frac{2\pi m}{qB}$
So, $T\alpha \frac{m}{q}$ (Taking B as same)
So, $\alpha -particle$ has 4 times mass of proton and 2 times charge of proton.
So, $T\alpha =\frac{4m}{2q}$ (taking mass of proton = m, Charge of proton = q)
So, $T\alpha =2Tp$