When light of wavelength, 1 , is incident on a certain photoelectric cathode, no

Question

When light of wavelength, 1, is incident on a certain photoelectric cathode, no
electrons are emitted, no matter how intense the incident light is. Yet, when light of wavelength2 < 1 is incident, electrons are emitted, even when the incident light has a very low intensity.
a) Explain why this happens. (10 pts)
b) If all you had was a light source with wavelength 1, what could you change so that electrons would be emitted? Explain your answer using your knowledge of the Photoelectric effect. (5 pts)

Explanation / Answer

a) Every material has a property called the work function, which is the minimum energy a photon must have in order to cause the emission of an electron. The longer wavelength means it has less energy, so the photon must have had less energy than the value of the work function, so the electrons were not emitted. b) Based on the photoelectric effect, you still need the exact value of energy in the photon to emit electrons, so there is nothing that you can do with the longer wavelength to cause the emission of electrons

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