Threshold Frequency vs Work Function
Work function and threshold frequency are two terms associated with the photoelectric effect. The photoelectric effect is a widely used experiment to demonstrate the particle nature of waves. In this article, we are going to discuss what photoelectric effect is, what work function and threshold frequency are, their applications, the similarities and differences between work function and threshold frequency.
What is threshold frequency?
To properly understand the concept of threshold frequency, one must first understand the photoelectric effect. Photoelectric effect is the process of the ejection of an electron from a metal in the case of incident electromagnetic radiations. The photoelectric effect was first properly described by Albert Einstein. The wave theory of light failed to describe most of the observations of the photoelectric effect. There is a threshold frequency for the incident waves. This indicates that no matter how intense the electromagnetic waves are electrons would not be ejected unless it has the required frequency. The time delay between the incidence of light and the ejection of electrons is about a thousandth of the value calculated from the wave theory. When light exceeding the threshold frequency is produced, the number of emitted electrons depends on the intensity of the light. The maximum kinetic energy of the ejected electrons depended on the frequency of the incident light. This led to the conclusion of the photon theory of light. This means that the light behaves as particles when interacting with matter. The light comes as small packets of energy called photons. The energy of the photon only depends on the frequency of the photon. This can be obtained using the formula E = h f, where E is the energy of the photon, h is the Plank constant, and f is the frequency of the wave. Any system can absorb or emit only specific amounts of energy. The observations showed that the electron will absorb the photon only if the energy of the photon is enough to take the electron to a stable state. The threshold frequency is denoted by the term ft.
What is Work Function?
The work function of a metal is the energy corresponding to the threshold frequency of the metal. The work function is usually denoted by the Greek letter φ. Albert Einstein used the work function of a metal to describe the photoelectric effect. The maximum kinetic energy of the ejected electrons depended on the frequency of the incident photon and the work function. K.E.max= hf – φ. The work function of a metal can be interpreted as the minimum bond energy or the bond energy of the surface electrons. If the energy of the incident photons is equal to the work function, the kinetic energy of the released electrons will be zero.
What is the difference between Work Function and Threshold Frequency?
• Work function is measured in joules or electron volts, but the threshold frequency is measured in hertz.
• Work function can be directly applied to the Einstein equation of the photoelectric effect. To apply the threshold frequency, the frequency must be multiplied by the plank constant in order to obtain the corresponding energy.