If it takes 4.68 x 10 -19 J of energy to eject an electron from the surface of a certain metal, calculate?

Question

If it takes 4.68 x 10 -19 J of energy to eject an electron from the surface of a certain metal, calculate the longest possible wavelength, in nanometers, of light that can ionize the metal.

Answer 1

For a photon, E = hf = hc/λ, where h is Planck's constant, and λ is the wavelength.

E = hc/λ
λ = hc/E
λ = h * 299,792,458 m/s / 4.68 x 10^-19 J
h = 6.6260693 * 10^-34 J*s
λ = 6.6260693 * 10^-34 J*s * 299,792,458 m/s / 4.68 x 10 -19 J
λ = 4.24 * 10^ -7 m (solution)