4. In the photo-electric effect, the minimum energy required for a single photon

Question

4. In the photo-electric effect, the minimum energy required for a single photon to be able to free an electron is called the work function, which we will denote as . a) 2.75 eV for a particular target, what is the maximum wavelength that a photon can have while still being able to free an electron from the target? Express your answer in nm. b) What would be the kinetic energy of the electron that is freed by the photon in part a)? Express your answer in eV c) If we double the frequency of the photon from part a), what would be the kinetic energy of the freed electron? Express your answer in eV

Explanation / Answer

a) For = 2.75 eV as the work function, the wavelength required will be

= h c/ => = h c/E = 501 nm

b) As is the work function, the emitted electrons will have zero kinetic energy.

c) When the frequency is doubled, the energy will be doubled. The extra energy will be obtained by the electron as the kinetic energy. Hence, the KE = 2 x 2.75 - = 2.75 eV.

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