# Exercise 3 | Early Quantum Theory

1) What is the wavelength of a photon with an energy of 8.26 x 10-19 J?

2) How much energy does a mole of photons with a wavelength of 550 nm? What is the frequency?

1) E = hν = $\frac{\mathrm{hc}}{\mathrm{\lambda }}$ ⇒ λ = $\frac{\mathrm{hc}}{\mathrm{E}}$ = 2.41 x 10-7 m = 241 nm

2) E = nhν  with n = number of photons = 1 mole of photons = 6.022 x 1023 photons
E = $\frac{\mathrm{nhc}}{\mathrm{\lambda }}$ = 2.18 x 105 J
ν = $\frac{\mathrm{c}}{\mathrm{\lambda }}$ = 5.45 x 1014 s-1