વેગમાનના સંરક્ષણ નો ઉપયોગ કરતાં \( \,{p_{atom}}\,\, = \,\,{p_{photon}}\, = \,\,\frac{h}{\lambda }\)
\( \Rightarrow \,\,K.E.\,\, = \,\,\frac{{p_{atom}^2}}{{2m}}\,\, = \,\,\frac{{{h^2}}}{{2\,{\lambda ^2}m}}\)
જ્યાં \(m\,\, = \) હીલિયમનું દળ
\( = \,\,\,\frac{{4\,\, \times \,\,1{0^{ - 3}}kg}}{{6.023\,\, \times \,\,{{10}^{23}}}}\,\, = \,\,0.664\,\, \times \,\,{10^{ - 26}}\,\,kg\)
\(\therefore \,\,\,K.E.\,\, = \,\,\frac{{{{(6.6\,\, \times \,\,{{10}^{ - 34}})}^2}}}{{2\,\, \times \,\,{{({{10}^{ - 11}})}^2} \times \,6.64\,\, \times \,\,{{10}^{ - 27}}}}\,\,J\,\, = \,\,3.3\,\, \times \,\,{10^{ - 19}}\,\)
\( = \,\,2\,eV\)
(he $=1245 \mathrm{eVnm}, \mathrm{e}=1.6 \times 10^{-19} \mathrm{C}$ આપેલ છે.)