Energy of a green-light photon

Problem

A green-light photon has wavelength $\lambda = 500\;\text{nm}$. Calculate its energy $E = hc/\lambda$ ($h = 6{,}63\cdot 10^{-34}\;\text{J·s}$, $c = 3{,}0\cdot 10^8\;\text{m/s}$).

Solution

Applying the Planck–Einstein relation $E = hc/\lambda$ in SI units:

$E = \frac{hc}{\lambda} = \frac{6{,}63\cdot 10^{-34}\cdot 3{,}0\cdot 10^8}{500\cdot 10^{-9}} = \frac{1{,}989\cdot 10^{-25}}{5{,}0\cdot 10^{-7}}$

$\ev{E \approx 4{,}0\cdot 10^{-19}\;\text{J} \approx 2{,}48\;\text{eV}}$

(Check in eV: $E = 1240/500 \approx 2{,}48\;\text{eV}$, a typical energy for visible photons.)

Collegamenti

Argomenti: Quantum physics Concetti: Photon