Question

The wavelength of the most energetic X-ray emitted when a metal target is bombarded by $40$ keV electron is approximately:

• A. $300\stackrel{0}{\text{A}}$
• B. $10\stackrel{0}{\text{A}}$
• C. $4\stackrel{0}{\text{A}}$
• D. $0.31\stackrel{0}{\text{A}}$

Answer 1

The correct option is D $0.31\stackrel{0}{\text{A}}$

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

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

$\lambda =\frac{6.63\times {10}^{-34}\times 3\times {10}^8}{1.602\times {10}^{-19}\times 100\times {10}^3}$

$\lambda =12.415\times {10}^{-12}$

$\lambda =0.124\stackrel{0}{\text{A}}$