Wave Particle Duality of Light

Wave Particle Duality of Light

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The Wave Particle Duality of Light is a big deal in quantum theory. Basically, it means that light like both a wave and a particle. This idea doesn't just apply to tiny elementary particles - even bigger things like atoms and molecules can show these two properties. So, it's not just light that's got this dual nature, but matter too.

What is the wave-particle duality of light?

The concept of the wave-particle duality of light says that light possesses both wave and particle properties, even though we cannot observe both at the same time.

Light mostly acts as a wave, but it may also be thought of as a collection of small energy packets known as photons. Photons have no mass but convey a set quantity of energy.

The amount of energy carried by a photon is directly proportional to the photon's frequency and inversely proportional to its wavelength. To calculate a photon's energy, we use the following equations:


E =   h c  λ


E   is the photon's energy (Joules).λ is the photon's wavelength (meters).c  is the speed of light in a vacuum (299,792,458 meters per second).h  is the  Planck constant : 6.62607015 * 10 ^ -34 (m ^ 2kgs ^ -1).


Wave-Particle Duality of Light: Wave properties of light

The four classical light properties as a wave are reflection, refraction, diffraction, and interference.

Two-slit interference pattern
Two-slit interference pattern

History of Wave-Particle Duality

Current scientific thinking, as advanced by Max Planck, Albert Einstein, Louis de Broglie, Arthur Compton, Niels Bohr, Erwin Schrödinger, and others, holds that all particles have both a wave and a particle nature. This behavior has been observed not just in elementary particles but also in complex ones, such as atoms and molecules.

In 1900, Max Planck formulated what is known as  Planck's radiation law to explain the spectral-energy distribution of a blackbody's radiation. A  blackbody is a hypothetical substance, which absorbs all radiant energy that strikes it, cools to an equilibrium temperature, and re-emits the energy as rapidly as it receives it.

Given Planck's constant (h = 6.62607015 * 10 ^ -34), the speed of light (c = 299792458 m / s), the Boltzmann constant (k = 1.38064852 * 10 ^ -23m ^ 2kgs ^ -2K ^ -1), and the absolute temperature (T), Planck's law for energy Eλ emitted per unit volume by a cavity of a blackbody in the wavelength interval from to λ + Δλ may be expressed as follows:

E λ  =   8 π h c   λ 5   ·  1  e x p ( h c / k T λ ) - 1

Most of the radiation emitted by a blackbody at temperatures up to several hundred degrees is in the infrared region of the electromagnetic spectrum. At increasing temperatures, the total radiated energy rises, and the intensity peak of the emitted spectrum changes to shorter wavelengths, resulting in visible light being released in greater amounts.

While Planck used atoms and a quantized electromagnetic field to solve the ultraviolet crisis, most modern physicists concluded that Planck's model of 'light quanta' had inconsistencies. In 1905, Albert Einstein took Plank's blackbody model and used it to develop his solution for another massive problem: the photoelectric effect. This says that when atoms absorb energy from light, electrons are emitted from atoms.

Einstein's explanation of the photoelectric effect: Einstein provided an explanation for the photoelectric effect by postulating the existence of photons, quanta of light energy with particulate qualities. He also stated that electrons could receive energy from an electromagnetic field only in discrete units (quanta or photons). This led to the equation below:

E = h f


where  E   is the amount of energy,  f   is the frequency of light (Hertz), and his  Planck's constant (6.626 * 10 ^ -34).

Wave-Particle Duality of Light: De Broglie's hypothesis

In 1924, Louis-Victor de Broglie came up with de Broglie's hypothesis, which made a big contribution to quantum physics and said that small particles, such as electrons, can display wave properties. He generalized Einstein's equation of energy and formalized it to obtain the wavelength of a particle:

λ =  h  m v

where λ is the particle's wavelength,  h   is Planck's constant (6.62607004 * 10 ^ -34 m ^ 2 kg / s), and m is the mass of the particle moving at a velocity v.

Wave-Particle Duality of Light: Heisenberg's uncertainty principle

∆ x ∆ p ≥  h  4 π

Wave-Particle Duality - Key takeaways

Wave-particle duality is a concept that explains how both light and matter can act like both waves and particles, even though we can't observe both at the same time. When we think of light, we usually think of it a wave, but it can also be made up of tiny energy packets called photons. The properties of wave motion, like amplitude, wavelength, and frequency, can be used to measure light. Light also shows other wave properties, like reflection, refraction, diffraction, and interference. The photoelectric effect is another important concept in this area. It describes how electrons can be released from a metal's surface when it's hit by light with a certain frequency. These electrons are called photoelectrons. Finally, there's the uncertainty principle, which states that we can't accurately measure both the position and velocity of something at the same time, even in theory.

Wave Particle Duality of Light

What is both a wave and a particle?

 Light can be understood both as a wave and a particle. 

Who discovered wave-particle duality?

Louis de Broglie suggested that electrons and other discrete pieces of matter, which had formerly only been thought of as material particles, had wave characteristics, such as wavelength and frequency.

What is wave-particle duality definition?

Light and matter have properties that are both wavelike and particle-like.

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