The wave length of light from the spectral emission line of sodium is $589\;nm$ . Find the kinetic energy at which an electron would have the same de- Brojlie wavelength . given $(h= 6.6 \times 10^{-34}\;Js, me= 9 \times 10^{-31}kg, \; m_n =1.66 \times 10^{27}\;kg)$