Question

The wavelength of $K_ \alpha $ line in copper is 1.5 $ \overset{o}{\mathop{\text{A}}}\, $ . The ionization energy of K electron in copper is

• A. $ 11.2\times {{10}^{-17}}J $
• B. $ 12.9\times {{10}^{-16}}J $
• C. $ 1.7\times {{10}^{-15}}J $
• D. $ 10\times {{10}^{-16}}J $

Answer 1

Answer: (B)

Required ionisation energy $ =\frac{hc}{\lambda } $
$ =\frac{6.6\times {{10}^{-34}}\times 3\times {{10}^{8}}}{1.54\times {{10}^{-10}}} $
$ =12.9\times {{10}^{-16}}J $