Question

Calculate the energy in eV of 1 mole of photons having a wavelength of 331 nm.

• A. 5.37 eV
• B. 6.88 eV
• C. 2.58 eV
• D. 3.75 eV

Answer 1

The correct option is D 3.75 eV

According to Planck's Quantum theory,
E = $hv$ = $\frac{hc}{\lambda }$
where h = Planck's constant
$v$ is the frequency of the photon
$\lambda$ = wavelength of the photon = 331 nm = $331\times {10}^{-9}$ m
So, E = $\frac{6.626\times {10}^{-34}\times 3\times {10}^8}{331\times {10}^{-9}}$
E = $6.0\times {10}^{-19}$ J
We know, 1 eV = $1.6\times {10}^{-19}$ J
$\therefore$ E = $\frac{6.0\times {10}^{-19}}{1.6\times {10}^{-19}}$ = 3.75 eV