A Level Physics Practice Exam

What is a key factor affecting the emission of electrons in the photoelectric effect?

1. Type of atom in the material

2. Temperature of the electrons

3. Intensity of radiation

4. Frequency of the incident radiation

The correct answer is: Frequency of the incident radiation

The frequency of the incident radiation is the key factor affecting the emission of electrons in the photoelectric effect. This phenomenon occurs when light or electromagnetic radiation strikes a metal surface and causes the ejection of electrons from that surface. According to the theory of the photoelectric effect, it is the energy of the incoming photons that determines whether or not an electron can be emitted. The energy of a photon is directly proportional to its frequency, described by the equation \(E = hf\), where \(E\) is the energy of the photon, \(h\) is Planck's constant, and \(f\) is the frequency. For an electron to be emitted, the energy of the incoming photons must be greater than or equal to the work function of the material, which is the minimum energy required to remove an electron from the surface. If the frequency is below a certain threshold (the threshold frequency), no electrons will be emitted, regardless of the intensity of the radiation. Thus, the frequency of the incident radiation is crucial because it dictates whether the photons have enough energy to overcome the work function and lead to electron emission. In contrast, the type of atom in the material can influence the work function value but does not directly affect the fundamental mechanism of emission