Electrons with energy 80 keV are incident on the tungsten target of an X-ray tube. K shell electrons of tungsten have –72.5 keV energy. X-rays emitted by the tube contain only

$$\begin{gathered} {\lambda }_0=\frac{hc}{E}=1.55\times {10}^{-11}m \\ \therefore {\lambda }_0=1.55\stackrel{\text{0}}{\text{A}} \end{gathered}$$

Which is the minimum wavelength of continuous X-rays which carry energy equivalent to energy of incident electrons. Now, as the energy of incident radiation is more than that of on the continuous spectrum. Therefore, (D) is the answer