First of all, we can calculate the frequency of the photon, which is related to the wavelength by the following equation:
\(f= \frac{c}{\lambda}\)
where c is the speed of light and \(\lambda=670.8 nm=670.8 \cdot 10^{-9} m\) is the photon wavelength. Substituting into the formula, we find the frequency
\(f= \frac{c}{\lambda}= \frac{3 \cdot 10^8 m/s}{670.8 \cdot 10^{-9} m}=4.47 \cdot 10^{14} Hz\)
Now we can find the energy of the photon with the following equation:
\(E=hf\)
where h is the Planck constant. Substituting numbers, we find
\(E=hf=(6.6 \cdot 10^{-34}Js)(4.47 \cdot 10^{14} Hz)=2.95 \cdot 10^{-19} J\)
