Question

The increasing order for the value of charge/mass for electron (e), proton (p), neutron (n) and alpha particle $ (\alpha ) $ is:

• A. $ e < p < n < a $
• B. $ n < p < e < \alpha $
• C. $ n < p < \alpha < e $
• D. $ n < \alpha < p < e $

Answer 1

Answer: (D)

Find e/m (charge/mass) of all the given particles and then arrange them in given order.
(i) e/m of electron $ =\frac{1.6\times {{10}^{-19}}}{9.1\times {{10}^{-28}}}=0.175\times {{10}^{9}} $
(ii) e/m of proton $ =\frac{1.6\times {{10}^{-19}}}{1.673\times {{10}^{-24}}}={{10}^{5}} $
(iii) e/m of neutron $ =\frac{0}{1.673\times {{10}^{-24}}}=0 $
(iv) e/m of $ \alpha - $ particle $ =\frac{2\times 1.6\times {{10}^{-19}}}{4\times 1.67\times {{10}^{-24}}}=0.5\times {{10}^{5}} $
$ \therefore $ The correct order is $ n<\alpha