In a photoelectric effect experiment, a metal sample is illuminated by 10.0 mW o

Question

In a photoelectric effect experiment, a metal sample is illuminated by 10.0 mW of ultraviolet light of wavelength 240 nm. It is observed that 250,000 photoelectrons are ejected from the metal each second, with kinetic energies from zero to 2.20 eV.

1. What is the work function of this metal, in eV?

2. What is the longest wavelength of light that can knock electrons out of this metal?

Please show all work. I know this question is somewhere else, but it is hard to follow. I would appreciate genuine answers.

Explanation / Answer

incident photon energy = hc / wavelength = 5.176 eV

1. Work fn = incident energy - max KE = 2.976 eV

2. wavelength = hc/E

Where E = 2.2 eV = 2.2 * 1.6 *10^-19 J

So, wavelength = 1242.375 nm

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