Question

The wavelength of $K_{\alpha }$ X-rays produced by an X-ray tube is $0.76\AA$. The atomic number of anode material is

• A. 82
• B. 41
• C. 20
• D. 10

Answer 1

The correct option is B 41

For $K_{\alpha }$X-ray line
$\frac{1}{{\lambda }_{\alpha }}=R{\left(Z-1\right)}^2\left(\frac{1}{1^2}-\frac{1}{2^2}\right]=\frac{3R}{4}{\left(Z-1\right)}^2$
$\frac{1}{0.76\times {10}^{-10}}=\frac{3}{4}\times 1.09\times {10}^7{(Z-1)}^2\Rightarrow {\left(Z-1\right)}^2\approx 1600\Rightarrow Z-1=40Z=41$