Question

How does the photoelectric effect support particle theory?

Answer 1

Hint: The photoelectric effect may be defined as the ejection of electrons from the surface of a metal under the influence of striking photons. The effect is readily shown by cesium since the electrons are most loosely held because of low ionization enthalpy of the metal.

Complete step by step answer:
Let’s understand the particle theory of matter. This theory of matter states that matter consists of many small particles which exist in a state of continuous motion.

Photoelectric effect can be explained with the help of particle nature of light which consists of a stream of photons. This was proposed by Einstein in 1905. Each proton is a source of energy. Actually, electrons are held by the nuclei of the metal atoms by a certain force called binding force. In order that the electrons may escape from the metal surface, they have to be supplied certain energy to overcome this binding energy. The job is performed by photons which must contain a minimum energy known as threshold energy $\left( {E = h{v_0}} \right)$ to counter this binding energy. Here, E is energy, v is frequency and ${v_0}$ is called threshold frequency. The threshold energy is also known as work function $\left( {{W^0}} \right)$. Now, it is just possible that the energy (hv) of the incident or striking photons may be more than the threshold energy needed to bring about the photoelectric effect. Under this circumstance, the extra energy is taken up as kinetic energy by the electrons that are ejected. In general,

Energy of incident photon (hv)= work function (h${v_0}$)+ Kinetic Energy of emitted photon

Note: It is to be noted that light and other electromagnetic radiations have dual nature. These are wave nature and particle nature. Certain phenomena like interference and diffraction could be explained on the basis of wave nature while a few others like black body radiations and photoelectric effect could be explained by the particle nature.