A Level Physics Practice Exam

What does the kinetic energy of emitted electrons in the photoelectric effect depend on?

1. The frequency of radiation and the work function

2. The mass of the electrons and the intensity of radiation

3. The wavelength of radiation and ambient temperature

4. The charge of the electrons and the type of atom

The correct answer is: The frequency of radiation and the work function

In the context of the photoelectric effect, the kinetic energy of emitted electrons is fundamentally influenced by the frequency of the incident radiation and the work function of the material from which the electrons are being emitted. When light of a certain frequency strikes the surface of a metal, it can transfer energy to electrons. The energy of the incoming photons is determined by their frequency. According to the equation \(E = hf\), where \(E\) is the energy of the photon, \(h\) is Planck's constant, and \(f\) is the frequency, it becomes evident that higher frequency photons carry more energy. The work function is the minimum energy required to liberate an electron from the surface of the material. If the energy of the incoming photon exceeds the work function, the excess energy is converted into the kinetic energy of the emitted electron. Thus, the kinetic energy can be expressed as: \[ K.E. = hf - \phi \] where \(K.E.\) is the kinetic energy of the emitted electron and \(\phi\) is the work function of the material. This relationship demonstrates that as the frequency of the radiation increases (assuming it is above the work function), the kinetic energy of the emitted electrons also