Question

The intensity of $X$ -rays from a Coolidge tube is plotted against wavelength as shown in the figure. The minimum wavelength found is ${\lambda }_c$ and the wavelength of the $K_{\alpha }$ line is ${\lambda }_k$. As the accelerating voltage is increased

• A. $\left({\lambda }_K-{\lambda }_C\right)$ increases
• B. $\left({\lambda }_K-{\lambda }_C\right)$ decreases
• C. ${\lambda }_K$ increases
• D. ${\lambda }_K$ decreases

Answer 1

Answer: (A)

Wavelength ${\lambda }_K$ is independent of the accelerating voltage $(V)$, while the minimum wavelength ${\lambda }_C$ is inversely proportional to $V$. Therefore as $V$ increases, ${\lambda }_k$ remains unchanged whereas ${\lambda }_c$ decreases or ${\lambda }_k-{\lambda }_c$ will increase.