Question

The ratio of the e/m value of a proton and an $\alpha$-particle is:

• A. $2:1$
• B. $1:1$
• C. $1:2$
• D. $1:4$

Answer 1

The correct option is A $2:1$

For a proton ${(}_1^{1}H),\frac{e}{m}=\frac{1}{1}$
For an $\alpha$-particle ${(}_2^{4}He),\frac{e}{m}=\frac{2}{4}=\frac{1}{2}$
$\frac{{\left(\frac{e}{m}\right)}_p}{{\left(\frac{e}{m}\right)}_{\alpha }}=\frac{\frac{1}{1}}{\frac{1}{2}}=2:1$