The work function of the electron from silver 7, 85 * 10 ^ (- 19) J. Determine the wavelength

The work function of the electron from silver 7, 85 * 10 ^ (- 19) J. Determine the wavelength of the red border of the photoelectric effect for silver.

1. Let us write down the Einstein equation for the photoelectric effect:
h * ν = A + Tmax, where A is the work function of an electron from the metal, Tmax is the maximum kinetic energy of photoelectrons, h * ν is the energy of a photon.
2. At the cutoff frequency νcr, Tmax = 0
So the work function of an electron is determined by the expression:
A = h * νcr
h = 6.63 * 10 ^ -34 J * c- Planck’s constant.
3. The radiation frequency is found from the expression:
ν = c / λ, where c is the speed of light c = 3 * 10 ^ 8 m / s, λ is the wavelength.
4. Substitute the frequency into the formula from point 2 .:
A = h * νcr = h * s / λ
Let us express the wavelength from this expression:
λ = h * s / A
5.Substitute the numerical values ​​and find the wavelength:
λ = h * s / A = 6.63 * 10 ^ -34 * 3 * 10 ^ 8 / 7.85 * 10 ^ -19 = 253 * 10 ^ -9 m.
Answer: the wavelength of the red border of the photoelectric effect is 253 * 10 ^ -9 m or 253 nm.