Question

The ratio of $e / m$ of a proton to that of an $\alpha$ - particle is:

• A. $1: 5$
• B. $1: 2$
• C. $1: \frac{1}{4}$
• D. $1: \frac{1}{2}$

Answer 1

Answer: (D)

Required ratio $=\frac{\left(\frac{q_{p}}{m_{p}}\right)}{\left(\frac{q_{\alpha}}{m_{\alpha}}\right)}=\frac{q_{p}}{q_{\alpha}} \times \frac{m_{a}}{m_{p}}=\frac{q_{p}}{2 q_{p}} \times \frac{4 m_{p}}{m_{p}}$
$=2=2: 1 $
$=1: \frac{1}{2} $