Question

Calculate the wavelength of a photon having an energy of 2 eV

• A. $6.20\times {10}^3$ nm
• B. $6.21\times {10}^3\stackrel{\circ }{A}$
• C. $4.41\times {10}^3$ nm
• D. $4.41\times {10}^3\stackrel{\circ }{A}$

Answer 1

The correct option is B $6.21\times {10}^3\stackrel{\circ }{A}$

$1eV=1.6\times {10}^{-19}J$
From planck's quantum theory, E = $\frac{hc}{\lambda }$
where E = energy of the photon
$\lambda$ = wavelength of the photon
So, $\lambda =\frac{hc}{E}=\frac{6.626\times {10}^{-34}\times 3\times {10}^8}{2\times 1.6\times {10}^{-19}}=6.21\times {10}^{-7}m$
$\lambda =6.21\times {10}^3\stackrel{\circ }{A}$