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Photoelectric Effect [ Light is a PARTICLE]

In the previous entry, we said that light is a WAVE based on its characteristics of showing wave phenomena. Knowing that, light is also a PARTICLE. Later in this writing, we will figure out how light can be also concluded as a particle.

Photoelectric Effect

Photoelectric Effect is the emission of electrons (called photoelectrons) from a metal surface when an incident light strikes the surface with enough energy/frequency.

The photoelectric effect is represented by the Einstein's Photoelectric Effect equation:


This equations consists of 3 terms which represent 3 items in the figure above that are , E is for the incident light , Wo is for the Metal and Kmax is for the Photoelectrons.

The incident light energy must be bigger than the work function of the metal. Work function is basically the energy possessed by the electrons in the metal. Hence, to free these electrons from the metal , the incident light must have enough energy to displace the electrons.

 The incident light frequency must be bigger than the threshold frequency. threshold frequency is basically the frequency possessed by the electrons in the metal (electrons vibration). Hence, to free these electrons from the metal , the incident light must have enough frequency to displace the electrons.

Light as a particle

By the Photoelectric Effect experiment, Einstein found out that light that strikes the metal with different frequency will either emits or does not emit electrons from the metal surface. If we have blue and red light of the same brightness strike the metal, red light gives off no electrons! Why? This is because red light has lower energy (due to its lowest frequency).

 It is proven that light cannot behave as a wave in this case!!! If it is a wave, the emission of photoelectrons will depends on the amplitude of wave (incident light) as the amplitude is directly proportional to energy.

The physicist Max Planck suggested that light comes in a discrete bundle, called quanta (PARTICLE). Then, Einstein suggested that each quantum (singular of quanta) of light has enough energy to escape one electron from the metal. This light particle is named as PHOTON. The emission of the photoelectrons does not depend on how many photons (light) strikes the metal but it depends on the energy brought by each photon.

Thank you,
Mdm Ummi Atiah KMPk
~ May it Benefits You ➽💕



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