A Level Physics Practice Exam

What is the significance of the work function in the photoelectric effect?

1. It is the maximum energy that photons can have

2. It is the minimum energy needed to remove an electron from an atom

3. It indicates the type of radiation emitted

4. It is the energy required to ionize an atom completely

The correct answer is: It is the minimum energy needed to remove an electron from an atom

The significance of the work function in the photoelectric effect lies in its definition as the minimum energy required to remove an electron from the surface of a material, typically a metal. This energy barrier must be overcome by the incoming photons for the photoelectric effect to occur, where electrons are emitted when light shines on the surface of the material. When a photon strikes the surface, it must have energy equal to or greater than the work function for an electron to be liberated. If the energy of the photon is equal to the work function, the electron will be emitted with zero kinetic energy; if it is greater, the excess energy is converted into the kinetic energy of the emitted electron. This concept is crucial in understanding how light interacts with matter and forms the basis for the photoelectric effect, ultimately supporting the particle theory of light, which led to the development of quantum mechanics. The work function varies between different materials, which is why different substances respond differently to the incidence of light. Options that mention maximum energy, type of radiation emitted, or the energy required for complete ionization do not accurately reflect the direct role that the work function plays in this specific phenomenon. It's focused solely on the energy threshold needed to liberate an electron from an atom in a