Question

Calculate the maximum wavelength, Imax, of electromagnetic radiation that could eject electrons from the surface of copper, which has a work function of 7.26 x 10-19 J. Imax = 2.74 x10-7 If the maximum speed of the emitted photoelectrons is 3.94 x 10 m/s, what wavelength of electromagnetic radiation struck the surface and caused the ejection of the photoelectrons ? 2.81 x10-8 m

Answer 1

Here,

let the maximum wavelength is Lmax

for the energy of a photon

Energy = h * c/Lmax

7.26 *10^-19 = 6.626 *10^-34 * 3 *10^8/Lmax

solving for Lmax

Lmax = 2.74 *10^-7 m

the maximum wavelength is 2.74 *10^-7 m

-----------------------

let the wavelength is L

total energy = h * c/L

7.26 *10^-19 + 0.50 * 9.11 * 10^-31 * (3.94 *10^6)^2 = 6.626 *10^-34 * 3 *10^8/L

L = 2.55 *10^-8 m

the wavelength of em wave is 2.55 *10^-8 m