Question

Calculate the wavelength of a photon in Angstroms having an energy of $1$ electron-volt.

Answer 1

$1eV=1.602\times {10}^{-19}joule$;
$h=6.62\times {10}^{-34}J-s$, $c=3\times {10}^{8}m{s}^{-1}$
$\lambda =\frac{h\cdot c}{E}=12.42\times {10}^{-7}m=12.42\times {10}^3\mathring{A}$.