Question

Wavelength of a $2\text{keV}$ photon is,

• A. $620\mu m$
• B. $620\text{pm}$
• C. $620\text{nm}$
• D. $620\text{km}$

Answer 1

The correct option is B $620\text{pm}$

Energy of photon is, $E=\frac{hc}{\lambda }$
$\Rightarrow \lambda =\frac{hc}{E}=\frac{6.63\times {10}^{-34}\times 3\times {10}^8}{2\times {10}^3\times 1.6\times {10}^{-19}}$

$\therefore \lambda =6.215\times {10}^{-10}\text{m}\approx 620\text{pm}$

Hence, $\left(B\right)$ is the correct answer.