Question

When electromagnetic radiation at wavelength 300nm falls on the surface of sodium, electrons are emitted with a kinetic energy of $1.68\times {10}^{5}J{mol}^{-1}$. What Is the minimum energy needed to remove an electron from sodium?

Answer 1

We have to find ${h\nu }_o{h\nu }_o=h\nu -KE=\frac{h.C}{\lambda }-\frac{1.68\times {10}^{5}5/mol}{6.023\times {10}^{23}}{h\nu }_o=\frac{6.626\times {10}^{-34}\times 3\times {10}^8}{300\times {10}^{-9}m}-\frac{1.68\times {10}^5}{6.023\times {10}^{23}}=0.06626\times {10}^{-17}-0.2789\times {10}^{-18}=0.06626\times {10}^{-17}-0.02789\times {10}^{-17}{h\nu }_o=0.03837\times {10}^{-17}J$