Question

The wavelength of first spectral line of sodium is 5896 $\stackrel{0}{A}$ . What is the first excitation potential of sodium atom:

• A. 2.1volt
• B. 4.2 volt
• C. 1.5volt
• D. None of these

Answer 1

Answer: (A)

First excitation energy of sodium will be $E=hv=\frac{hc}{\lambda }=\frac{6.63\times {10}^{-34}\times 3\times {10}^8}{5896\times {10}^{-10}}$ $E=0.00337\times {10}^{-6}J=3.37\times {10}^{-19}J$ $E=\frac{3.37\times {10}^{-19}}{1.6\times {10}^{-19}}=2.1eV$ Hence, the first excitation potential of sodium atom is 2.1 volt.