The Photoelectric Effect Worksheet - Answer Key

 

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  1. What is the photoelectric effect?

    The photoelectric effect is a phenomenon that Einstein won a Nobel Prize for.  What Einstein showed, was that electrons could be emitted from the surface of a metal when light (at a minimum frequency) struck the metal surface.                                                                                             

  2. Four ideas to know about it

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    1. There is a minimum frequency needed to get electrons to emit.  An increase in intensity has no effect on electrons if the frequency of the light is below the threshold frequency.

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    2. Once the threshold frequency has been reached, an increase in light intensity will cause an increase in the number of electrons emitted.

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    3. The greater the frequency of light, the greater the kinetic energy of the emitted electron(s).

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    4. Demonstrated that light has a duality in nature.  Exhibiting both particulate and energy properties. The only way that these electrons could be knocked out is if the light has a particulate property to it that was able of “bumping” the electrons out.

     

     

  3. The big discovery of the photoelectric effect was the existence of photons.                                                      

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  4. Equation for the energy of a photon

    Ephoton = hν = hc/λ

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  5. Equation for kinetic energy of an electron

    KEelectron = hν – hνo = E – Eo
                                       

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  6. How do E, ν, and λ relate?

    As energy increases, do does the frequency.

     

    As energy increases, the wavelength decreases.

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  7. Microwave radiation has a wavelength on the order of 1.0 cm.  Calculate the frequency and the energy of a single photon of this radiation.  Calculate the energy of an Avogadro’s number of photons of the electromagnetic radiation.

    11.97 J/mol

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  8. The work function of an element is the energy required to remove an electron from the surface of the solid.  The work function for lithium is 279.7 kJ/mol.  What is the maximum wavelength of light that can remove an electron from an atom in lithium?

    λ = 428 nm

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  9. It takes 208.4kJ f energy to remove one mole of electrons from the atoms on the surface of rubidium metal.  If rubidium metal is irradiated with 254-nm light, what is the maximum kinetic energy the released electron can have?

    KEelectron = 4.37 x 10–19 J

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