Q. Increasing order (lowest first) for the values of $e/m$ for electron ($e$), proton ($p$), neutron ($n$) and $\alpha$-particles is

A) $e,p,n,\alpha$
B) $n,\alpha,p,e$
C) $n,p,e,\alpha$
D) $n,p,\alpha,e$
Explanation

(b)
$\frac{e}{m}for\ electron\ (e) = \frac{1.6 \times 10^{- 19}}{9.1 \times 10^{- 28}}$
$\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ = 1.758 \times 10^{8}$
$\frac{e}{m}for\ proton\ (p) = \frac{1.6 \times 10^{- 19}}{1.672 \times 10^{- 24}}$
$\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ = 9.56 \times 10^{4}$
$\frac{e}{m}for\ neutron\ (n) = \frac{0}{1.675 \times 10^{- 24}} = 0$
$\frac{e}{m}for\ \alpha - particle = \frac{2}{4} = 0.5$
Hence, the increasing order of $\frac{e}{m}$ is as
$n < \alpha < p < e$

Dr. Abubacker
Reviewed by Dr. Abubacker

Physics Educator & NEET/JEE Specialist

Ph.D. in Physics with 19+ years of teaching experience.