“Quantum Physics is the branch of Physics that deals with study of matter at small scale.”

**Introduction to Quantum mechanics**– A fundamental Theory in physics that describes the physical properties of matter at small scales is called Quantum mechanics. This is the only theory that gave foundation of all quantum physics together with Quantum Field Theory, Quantum chemistry , and Quantum information science and technology.

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### Why Quantum physics is So Weird?

Quantum Physics is totally different from Classical Physics because in classical Physics everything is present in Particle form but in Quantum Physics everything in the universe has wave nature as well as particle nature. This is the reason why we say Quantum Physics is so weird.

**The Foundation of quantum mechanics were established by : **

Max Planck, Niels Bohr, Werner Heisenberg, Louis de Broglie, Albert Einstein, Erwin Schrödinger, Satyendra Nath Bose and many others Scientists contributed in **foundation of Quantum Mechanics** .

Because of these Scientists Quantum Mechanics Became widely accepted theory during the first half of the 20th Century.

#### Most Famous Equation: Schrödinger’s Equation

The Schrödinger equation is a linear partial differential equation that describes the wave function of a quantum-mechanical system. This is an important result in quantum mechanics, and its discovery was an important milestone in the** development of quantum mechanics**. The equation is named after Irwin Schrödinger, who gave the equation in 1925, and published it in 1926, which resulted in his Nobel Prize in Physics in 1933.

The concept of a wave function is a fundamental signal of quantum mechanics; The wave function defines the state of the system at each spatial position and time.The solutions of Schrödinger’s equation describe not only molecular, atomic and sub-atomic systems, but also **macroscopic systems**, possibly the entire universe.

With the help of Schrödinger equation not only we can study quantum mechanical systems and make predictions but also we can study like Other aggregates of quantum mechanics include matrix mechanics, introduced by Werner Heisenberg, and the main integral formulation, developed by Richard Feynman. Paul Dirac incorporated matrix mechanics and the **Schrödinger equation into one formulation.**

#### Heisenberg’s Uncertainty Principle

In quantum mechanics,** Heisenberg’s uncertainty principle** is any kind of mathematical inequalities that provide a fundamental limit to the extent to which values for physical pairs of certain particles, such as position, x, and momentum, p, can occur. Predicted from initial conditions. Such variable pairings are known as complementary variables or canonically conjugated variables, and, depending on the interpretation, the uncertainty principle is limited to the extent that such conjugate properties retain their approximate meaning, Because the mathematical framework of quantum physics does not support the notion of simultaneous well. Defined conjugate properties expressed by a single value.

First introduced in 1927 by the **German physicist Werner Heisenberg,** the principle of uncertainty states that the more precisely the position of a particle, the more precisely its motion can be predicted from the initial conditions. And vice versa.

Since uncertainty theory is such a fundamental result in quantum mechanics, specific experiments in quantum mechanics regularly observe its aspects. However, some experiments may deliberately explore a particular form of uncertainty theory as part of their main research program. For example, superconducting or quantum optics systems involve tests of number-phase uncertainty relationships. Applications that rely on the principle of uncertainty for their operation include techniques with extremely low noise such as those required in **gravitational wave interferometers.**

#### Quantum Field Theory

A theoretical framework that combines classical field theory, special relativity and quantum mechanics in theoretical physics is called Quantum Field Theory.

(Note: Quantum Field Theory Doesn’t combines General relativity).

**Quantum field theory** is used in particle physics to construct physical models of sub-atomic particles and in condensed matter physics to construct models of quipiparticles.

Quantum field theory treats particles as quanta of their underlying fields, which are more fundamental than particles. The interactions between the particles are described by the interaction terms in the Lagrangian involving their respective regions. Each interaction can be visualized by** Feynman diagrams according to disturbance theory in quantum mechanics.**

#### Photoelectric Effect

The emission of electrons when electromagnetic radiation(light rays) hits a material is called photoelectric effect. The Electrons Which are emitted in this manner are called Photoelectrons. We study this phenomenon mainly in electronic physics and in fields of chemistry such as quantum chemistry and electrochemistry.

According to classical electromagnetic theory, **photoelectric effect** can be attributed to the transfer of energy from light to electron. From this point of view, a change in the intensity of light induces a change in the kinetic energy of electrons emitted from the metal.

According to this theory, sufficiently dim light is expected to show a time interval between the initial brightness of its light and the subsequent emission of an electron.

But experimental results were not associated with either of the two predictions made by classical theory. Instead, experiments have shown that electrons are disliked only by scattering of light when it reaches or **exceeds the threshold frequency.**

Because a low-frequency beam at high intensity cannot produce the energy required to produce photoelectrons such that if the energy of light were constant like a wave, Einstein proposed that a beam of light propagating from space Not a waveform, but rather a collection of **discrete wave packets (photons).**

#### Revolutionary Principles of Quantum Mechanics

-Wave Particle Duality

-Quantized properties

##### Wave Particle Duality –

Wave-particle duality is the concept in quantum mechanics that each particle or quantum unit can be described as a particle or a waveform. It expresses the inability of classical concepts “particles” or “waves” to fully describe the behaviour of **quantum-scale objects.**

Current scientific theories assume that all particles exhibit a wave nature and vice versa. This is proven with the help of the work done by many Scientists like Max Planck, Albert Einstein, Louis de Broglie, Arthur Compton, Niels Bohr, and many others.This phenomenon has been verified not only for elementary particles, but also for compound particles such as atoms and even molecules. For macroscopic particles, wave properties cannot usually be detected, due to their extremely short wavelengths.

##### Quantized properties–

Some properties, such as position, speed, and color, can sometimes occur only in a specific, set amount, much like a dial that “clicks” from number to number. This challenged a fundamental notion of classical mechanics, stating that such properties must exist on a smooth, continuous spectrum. To describe the idea that some properties ‘clicked’ like a dial with specific settings, scientists coined the term ‘quantized’.

#### About post

So far we have studied many terms like quantum field theory , dual nature of particles and many more and also we have learnt how quantum physics became the revolutionary theory in 20th century and also many scientists like max planck , albert einstein and co. contributed to this theory .You can read about.

I hope you guys have learnt many things from **Article: what is quantum mechanics ? **or quantum mechanical model and enjoyed as well. So thats it for today , If you want to read more then you can read other articles given below.