Question

When a beam of accelerated electrons hits a target, a continuous x-ray spectrum is emitted from the target. Which of the following wavelength is absent in the x-ray spectrum if the x-ray tube is operating at 40,000 volt?

• A. 1.5 $A^0$
• B. 0.5 $A^0$
• C. 0.25 $A^0$
• D. 1.0 $A^0$

Answer 1

The correct option is C 0.25 $A^0$

${\lambda }_{cutoff}=\frac{hc}{eV}$

$=\frac{20\times {10}^{-26}}{1.6\times {10}^{-19}\times 4\times {10}^4}$

$=3.125\times {10}^{-11}m$
$=0.31A^0$
so $\lambda >0.31A^0$

So, the answer is option (C).