Dual Nature of Radiation and Matter

The dual nature of radiation and matter tells, and every object has two nature associated with it that is a wave and particle. It is most commonly known as wave-particle duality. The wave nature of light came from Maxwell’s equations of electromagnetism and the experiment of generation and detection of electromagnetic waves done by Hertz. J. J Thompson was the first to determine the speed and charge of cathode ray particles. The dual nature of radiation and matter was proved by de Broglie and later confirmed by many experiments such as the David and Germer experiments. This was one of the biggest experiments ever conducted on the nature of radiation and matter. The duality of nature has solved many theories and explained many concepts. 

  Photoelectric effect

The photoelectric effect happens when electromagnetic radiation such as light hits the surface, which leads to the emission of electrons. The experiment can be affected by many factors such as intensity, potential, and frequency of the radiation which is being used.

Limitations of Photoelectric effect

• It doesn’t apply to all kinds of elements.
• It is limited to a specific temperature range and doesn’t work correctly beyond that. 

Laws of Photoelectric effect

• The frequency of the incident ray is directly proportional to the intensity of the incident ray
• There is a particular frequency called threshold frequency for a metal. It means below this threshold frequency, the photoelectric emission doesn’t occur.
• The kinetic energy of particles depends on the frequency of the incident ray

Photoelectric effect and wave theory of light

The wave nature of light was established in the nineteenth century, explaining many concepts such as the phenomenon of interference, polarisation, and diffraction. According to wave theory, electrons remain on the surface of the metal and continuously absorb radiant energy. Later on, some experiments showed that wave theory could not explain the photoelectric emission and its features. 

Particle nature of light: The photon

Einstein gave his theory of the photoelectric equation which means that electrons don’t absorb radiation continuously. Still, radiation energy is made up of discrete units called quanta of energy of radiation. He proved his theory and led to the following equation, which is commonly known as Einstein’s photoelectric equation. 

 KE = hv – hv0 

where KE is the kinetic energy of the photoelectron, h is Planck’s constant,  v is the frequency of the photon and v0 is the threshold frequency of material. The particle nature provides a valid reason for the behaviour of matter. It proves that particles of any matter are always moving, which can explain solid, liquid, and gas behaviour and properties. 

• The photoelectric effect gave  evidence that when light interacts with a matter, it behaves as a packet of energy that is hv. Each photon has its own energy E = hv and momentum p = hv/c, here c is the speed of light in a vacuum.
• Photons are not dependent on the intensity of the radiation used to strike the surface
• Photos are not deflected by magnetic and electric fields, which are neutral
• The total energy is conserved in photon-electron collisions
• The particle nature is depicted in experiments such as the photoelectric and coupon effects. 

Wave nature of matter

In later years, de Broglie established the wave nature of matter. The waves linked with the moving material particles are known as matter waves or de Broglie waves. 

The de Broglie wavelength is equal to λ = h/p. 

λ in the equation denoted the wave nature, and p denoted particle nature. Therefore, this equation solved both the nature of radiation and matter.

The wavelength calculated by the de Broglie hypothesis equation is not dependent on the charge and nature of the material. De Broglie’s experiment is the basis of all theories and modern quantum mechanics. The wave nature of electrons is utilised in the design of electron microscopes. 

Derivation Of De Broglie Equation

hf = mc2

As we know that f=c/ ƛ

It shows that hc/ ƛ=mc2 or ƛ = h/mc

If c=v; then ƛ=h/mv

We also know that the momentum of a particle is given by P= mv.

Therefore, ƛ=h/P.

Davisson and germer experiment

C.J Davisson and L.H Germer prove wave nature as per their experimental basis. Their experiment of electron diffraction arrangement confirms the wave nature of a beam of electrons and the de Broglie relation of wavelength. 

Later in 1988, the wave nature of a beam of electrons was again verified according to a double-slit experiment. The David and Germer experiment proved quantum mechanics ultimately.

Conclusion

The dual nature of radiation and matter is one of the most critical topics for science enthusiasts. It has solved many secrets of science. Because of the contribution of scientists like J.J. Thompon, de Broglie, Albert Einstein, this theory has become one of the biggest in science history. The wave nature of particles was discovered in the nineteenth century, which failed to explain light nature thoroughly. Later on, Albert Einstein discovered that light is nothing but a flow of energy packets called photons. The particle nature of radiation resolved some theories, such as the photoelectric and Compton effect. When David and Germer experimented on this, they were able to verify the dual nature of light and quantum mechanics.