Particle Nature of Light

Max Planck, a renowned German scientist, found in 1900 that particular types of metals ejected free electrons on contact with light. This experiment duly dealt with the photoelectric effect. Later on, Albert Einstein followed up on this experiment and discovered the particle nature of light. 

According to the observations of the former, wavelength of light had a massive influence on the ejected electrons. Also, the intensity of light has a direct impact on the electrons thus released. This fact pointed to the particle nature of light, which scientists previously considered as a wave. 

What is Particle Nature of Light? 

Until 1900, physicists assumed that light travelled in the form of waves. However, the photoelectric effect experiment suggested that it also possesses energy packets. Even other forms of electromagnetic energy comprise quanta of energy. 

What we call ‘photon’ today is nothing but constituents of energy. It, in turn, helped them to arrive at the particle nature of light. 

Moreover, scientists such as Albert Einstein observed a few highlights mentioned below.

  • Light sources with longer wavelengths contain lesser energy. This mainly refers to red and orange.

  • Contrarily, shorter wavelengths contain higher photons or packets of energy.

  • Consequently, wavelengths with higher energy content displaced a greater number of free electrons from metal surfaces.

This last observation helped Planck find out that the frequency of a source of light was directly proportional to the radiation of such electrons. 

What is Wave-Particle Duality?

As you know now, light contains photons or quanta of energy that assigns particle nature to it. Yet, it also comes in the form of waves, as the English scientist Thomas Young concluded through his Interference experiment. 

Therefore, you can recall the popular adage that “light is not only a wave but also a particle”. It refers to wave-particle duality as it is known today. Consequently, a photon possesses both the characteristics of a particle and wave. Scientists of that time arrived at this conclusion after conducting a series of quantum-mechanical experiments. 

As a result, the particle nature of light comes into play when it interacts with metals and irradiates free electrons. Contrarily, wave nature is prominent when seen in the field of propagation of light. Besides, photons assume an essential role in the electromagnetic propagation of energy. 

Now that you know the relation between photoelectric effect particle nature of light it is time to discuss some of the properties of photons. 

What are the Characteristics of Photons? 

Some of the most prominent characteristics of photon include the following – 

  • Photons are theoretically the smallest quantum of electromagnetic energy or radiation. Therefore, it forms the most basic constituent of light. 

  • The letter ‘c’ denotes it in mathematical expressions. Also, it possesses a speed of 2.99 X 108 m s-1. Besides, it is never restive, meaning that it is always in motion. On the other hand, photons travel at this speed only in a vacuum. 

  • The energy of a photon is equivalent to the product of oscillation frequency of light source and Planck’s constant. Therefore, E = hν, where ‘ν’ refers to frequency.  ‘h’ in this equation implies Planck’s constant, which is 6.62607004 X 10-34 m2kg/s. You can also express it as E = hv = hc/nλ, where λ stands for wavelength. 

  • However, the formula for a photon's momentum is p = hν/c. 

  • It is stable and lacks an electric charge. 

  • When a photon interacts with other subatomic particles like electrons, the successive phenomenon is referred to as the Compton effect. Besides, such a collision duly conserves total energy and momentum. Therefore, you can refer to it as an elastic collision, which preserves overall energy and momentum.  

  • It is also theoretically massless. However, these quantum packets transfer energy only on a collision with other particles. 

Therefore, the answer to the question of which phenomenon shows the particle nature of light is the photoelectric effect. 

Now that you have an idea about the particle nature of light, browse through our website to learn more about such intriguing topics. You can also download our Vedantu app to seek professional expertise and benefit from an interactive learning experience. 

FAQ (Frequently Asked Questions)

1. What is Light, What is its Nature?

Light implies a range of electromagnetic waves which the human eye can perceive. It has both wave and particle nature.

2. Name a Phenomenon Which illustrates the Particle Nature of Light?

 Photoelectric effect illustrates the particle nature of light.

3. Is Light a Particle or a Wave?

Light has a dual nature, which suggests that it comprises both wave and particle.