Physics - Modern Physics Question with Solution | TestHub

Energy of electron$\mathrm{H}{\mathrm{e}}^{+}$
$E_n$$=-13.6\frac{Z^2}{n^2} \mathrm{eV}; Z=2,\mathrm{ }n=3$
${\mathrm{E}}_3=\mathrm{ }-13.6\mathrm{ }{\left(\frac{2}{3}\right)}^2\times 1.6\times {10}^{-19} \mathrm{J}$
In Bohr's model energy,$E=- KE$
$E_3=-K{E}_3$
$\therefore 9.7\times {10}^{-19}=\frac{1}{2}m{v}^2$
$v=\mathrm{ }\sqrt{\frac{2\times 9.7\times {10}^{-19}}{9.1\times {10}^{-31}}}$
Velocity of electron in third orbit of$\mathrm{H}{\mathrm{e}}^{+}$is$1.46\times {10}^6 \mathrm{m} {\mathrm{s}}^{-1}$.