The wavelength of light from the spectral emission line of sodium is 589 nm. Find the kinetic energy at which
(i) an electron, and
(ii) a neutron, would have the same de-Broglie wavelength .

Explanation

Given, `lambda = 589 nm = 589xx10^(-9)m, m_(e )=9.1xx10^(-31)kg`.
`m_(n)=1.67xx10^(-27)kg, h = 6.62xx10^(-34)J-s`.
`KE_(e )=(P_(e )^(2))/(2m)=(h^(2))/(2m lambda^(2)) [because p_(e )=(h)/(lambda)] rArr KE_(e )=((6.63xx10^(-34))^(2))/(2xx(589xx10^(-9))^(2)xx9.1xx10^(_31))=6.96xx10^(-25)J`