A Level Physics Practice Exam

What factors contribute to the range of kinetic energies of emitted electrons in the photoelectric effect?

1. The type of metal and temperature

2. The frequency of the incident radiation only

3. The work function and photon energy

4. The intensity of the incident radiation only

The correct answer is: The work function and photon energy

The range of kinetic energies of emitted electrons in the photoelectric effect is fundamentally influenced by the work function of the material and the energy of the incident photons. When light shines on a metal surface, photons with energy can transfer that energy to the electrons in the metal. The energy of a photon is given by the equation \( E = hf \), where \( h \) is Planck's constant and \( f \) is the frequency of the incident light. If the energy of the photon is greater than the work function (the minimum energy required to remove an electron from the metal), the excess energy is converted into kinetic energy of the emitted electron. This means that the higher the frequency of the incident radiation, the greater the potential kinetic energy of the emitted electron can be, as long as it exceeds the work function. Thus, the work function determines the threshold energy needed for electrons to be emitted, while the energy of the incoming photons dictates how much kinetic energy the emitted electrons will possess beyond this threshold. When both factors are considered, we understand how they contribute to the varying kinetic energies of emitted electrons in the photoelectric effect.