Determine the work function of electrons from sodium if the red border of the photoelectric effect is 500nm.

λ = 500 nm = 500 * 10 ^ -9 m.
h = 6.62 * 10 ^ -34 J * s
C = 3 * 10 ^ 8 m / s.
A – ?
A = h * V, where h is Planck’s constant, V is the frequency of electromagnetic radiation, under the influence of which the photoelectric effect occurs.
C = V * λ, where C is the speed of electromagnetic radiation (speed of light), λ is the wavelength of electromagnetic radiation.
V = C / λ.
A = h * C / λ.
A = 6.62 * 10 ^ -34 J * c * 3 * 10 ^ 8 m / s / 500 * 10 ^ -9 m = 0.03972 * 10 ^ -17 J.
1J = 6.25 * 10 ^ 18 eV, then A = 0.03972 * 10 ^ -17 J * 6.25 * 10 ^ 18 eV = 2.4 eV.
Answer: the work function of electrons is A = 0.03972 * 10 ^ -17 J or 2.4 eV.