The wavelength of ${\mathrm{K}}_{\mathrm{\alpha }}$ line in copper is 1.54 $\stackrel{\mathrm{o}}{\mathrm{A}}$. The ionisation energy of K electron in copper in Joule is

• A

  $11.2\times {10}^{-27}$

• B

  $12.9\times {10}^{-16}$

• C

  $1.7\times {10}^{-15}$

• D

  $10\times {10}^{-16}$