Question

The energy of an X-Ray photon is 4 keV. Then its wavelength is

• A. 31 $A^0$
• B. 3.1 $A^0$
• C. 0.31 $A^0$
• D. 0.031 $A^0$

Answer 1

The correct option is B 3.1 $A^0$

$energy=\frac{hc}{\lambda }$
$4\times {10}^{3}eV=\frac{1240eV-nm}{\lambda }(hc=1290eV-nm)$
$\lambda =\frac{1240}{4\times {10}^3}nm$

$=310\times {10}^{-3}nm$
$=3100\times {10}^{-3}{A}^{\circ }$
$=3.1A^{\circ }$

So, the answer is option (B).