This theory spreads the idea that light traverses in tiny packets of energy. Each packet is termed the photon. The amount of energy possessed by each photon equals the product value of Planck’s constant and that particular photon’s frequency upon vibration. This quantum theory has introduced the dual nature of light. The photons exhibit characteristics that are similar to that of waves. But theoretically, photons are nothing but examples of physical matters that are built from subatomic particles like protons, neutrons, and electrons. So, here is the uniqueness. Let us discuss the reasons supporting the validity of the dual nature of light.

It is evident from the above portion, that one can witness the dual nature of light. Now let us know about both the particle and wave characteristics of light.

Light’s Wave theory

Interference and diffraction are two crucial phenomena that distinguish waves from particles. Through Maxwell, we came to know that light is an electromagnetic wave whose speed is identical to the individual units of light or the photons. In this regard, he also concluded that the frequency of a particular incident ray is proportional to its wavelength. This is mathematically represented by the given equation: v =c/λ. Here v stands for the frequency of the incident beam, while c stands for the speed of light and λ denotes the wavelength of that light. The electromagnetic waves have been segregated based on their wavelengths. For example, radio waves fall within the range 104- 1010of the electromagnetic spectrum. 

Dual nature of light–particle behavior 

The Photoelectric effect proves that light is composed of particles that possess energy. These packets of energy are denoted as photons. The Photoelectric effect is a natural phenomenon where electrons are dislodged from the metal surface when light hits the metal and influences the subatomic species, particularly the protons. To initiate the photoemission, the frequency of incident light must exceed the cut-off frequency. In other words, it must be enough to overcome the activation energy for a particular metal. The increase in frequency enhances the kinetic energy of the emitted photoelectrons. The kinetic energy graph however does not get affected by the intensity of the incident beam. 

On the other hand, we have witnessed the relationship between the intensity and wavelengths of different light rays. This is also applicable in the practical world where we notice greater energy in bigger ocean waves. As the intensity of light increases, there is no change in kinetic energy, although there is a discharge of more electrons. 

Each metal exhibits its critical frequency. If the frequency of the light beam is lower than this amount, the photoemission is not going to start. The critical frequency is signified by v0. Electrons are not dislodged if the frequency is lower than this value. From this, we can conclude that the kinetic energy can be perceived from the light frequency with the help of Planck’s constant. Planck’s constant is expressed by h. 

Value of h = 6.63 x 10-34 Joules seconds. 

From here we can derive the equation needed to calculate the kinetic energy of light waves. 

Ekin = hv – hv0. Here Ekin stands for the kinetic energy of the light waves. The energy of each photon particle is calculated with the product value of hv. The work function is the minimum amount of work required to eject the electrons. It varies from one metal to another. It is represented as hv0. 

The above equation is not valid every time, especially when light is regarded as a wave. The explanation is only persistent for the particle nature of light. Each particle should possess the minimum energy required to eject the electrons when they hit the metal surface. This further instigates the debate on the topic –is light a wave or particle.

Conclusion 

When we face the question – is light a wave or a particle the next time we should have a clear conclusion regarding this. Light behaves as an electromagnetic wave. Also, it is made up of structural units or photons which form the basis of study in quantum mechanics. The energy of each photon must be sufficient to execute photoemission. Their energy is calculated by the formula E photon = h v. The h in the formula stands for Planck’s constant, named after the famous German theoretical physicist Max Planck. The frequency of light waves is given by v. From this study we are now conscious of the dual nature of light.