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Quantum Mechanics is a discipline of Physics that deals with the study of matter and its interactions with energy on atomic and subatomic scales. It describes the properties of atoms and molecules along with their constituents namely electrons, protons, and neutrons.
- Quantum Mechanics describes the essential methodology of Physics.
- According to Classical Mechanics, objects exist in a specific place at a specific time.
- In quantum mechanics, objects exist in a haze of probability, i.e. they can be at point A, point B, and so on.
- The term ‘Quantum Mechanics was coined by Max Born, Wolfgang Pauli, and Werner Heisenberg in the early 1920s.
| Table of Content |
Key Terms: Quantum Mechanics, Quantum Theory, Quantum Physics, Matter, Electromagnetic Radiation, Quanta, Planck's Constant
What is Quantum Mechanics?
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Quantum Mechanics is a subfield of Physics that aims at understanding the properties of matter and objects in relation to their corresponding atomic and sub-atomic nature.
- It describes the characteristics of the atoms, protons, electrons, and neutrons in relation to each other.
- It also deals with electromagnetic radiation.
- Quantum Mechanics is a sub-discipline of the wider concept of Quantum Physics.
- It explains the working of the universe on a quantum scale.
- Quantum Energy refers to the least amount of energy that can exist in the universe.
- Therefore, quantum mechanics is the field that deals with the interaction of this energy with objects.
Quantum Mechanics
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| Relevant Concepts | ||
|---|---|---|
| Laser Light | Avogadro's Number | Wave Motion |
| Alpha Particle Mass | Magnetic Quantum Number | Modern Physics |
What is Quantum Theory?
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Quantum Theory is the theoretical study of matter and its properties in terms of atoms, protons, neutrons, electrons, etc. It defines various principles and theories for studying quantum mechanics and its applications.
| “Quanta refers to the lowest amount of energy as characterized by quantum theory.” |
There are three themes of quantum theory:
- Quantization of Energy and the Probabilistic Behavior of Energy Quanta
- Wave-particle Nature of Matter
- Planck's Constant
These three themes formed an interrelated set of ideas that lacked a system of mathematical expressions from which the values of quantities observed in experiments could be calculated. Quantum mechanics, thus, emerged as a necessity to bring mathematical clarity and solve the chaos of observations of the physical universe.
History of Quantum Mechanics
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Quantum Mechanics has developed over several decades, starting as a set of controversial mathematical explanations for experiments that were not explained by classical mechanics.
- The origins of quantum mechanics cannot be attributed to a single scientist.
- Multiple scientists and physicists laid a foundation for Quantum Mechanics and worked towards its popularity.
- It eventually gained acceptance and experimental verification between the late 1800s and 1930.
- The term “Quantum Mechanics” was given by a group of physicists namely Max Born, Wolfgang Pauli, and Werner Heisenberg in the early 1920s at the University of Göttingen.
Quantum Mechanics Timeline
Quantum Mechanics Timeline
The historical evolution of quantum mechanics is described below:
| Date of Emergence | Details |
|---|---|
| 1838 | A cathode beam was discovered by Michael Faraday. |
| 1859-1860 | The proclamation claiming the colder time of the year i.e. the winter statement of the dark body radiation came into existence. It was introduced by Gustav Kirchhoff. |
| 1877 | Ludwig Boltzmann proposed that the energy conditions of actual frameworks can be discrete in nature. |
| 1900 | Quantum speculation came into force, as found by Max Planck. This gave the indication for making the energy emanating atomic and sub-atomic frameworks. |
| 1920s | A group of physicists namely, Max Born, Wolfgang Pauli, and Werner Heisenberg coined the term “Quantum Mechanics”. |
Quantum Mechanics Formulas
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Quantum Mechanics Formulas are summarized in the following table:
| Quantity | Formula |
|---|---|
| Wavefunction Probability Density | \(\rho =\left |\Psi \right |^{2}=\Psi *\Psi\) |
| Photoelectric Equation | Kmax = hf + Φ |
| Hydrogen Atom Spectrum | \(\frac{1}{\lambda }=R(\frac{1}{n_{j}^{2}}-\frac{1}{n_{i}^{2}})\), nj<ni |
| Dipole Moment Potential | U = - μB = - μzB |
Quantum Mechanical Models
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Presently, the scientific world has only two acceptable and working models of quantum mechanics which are as follows
- The first model for understanding the application of quantum mechanics is the Bohr Model.
- The basis of the model of the Bohr is seen in terms of mathematics which is used for understanding complex structures.
- Another acceptable model is the Quantum Mechanical Model of an Atom which has its basis in quantum theory.
- This quantum theory ultimately defines the exact properties of matter over a period of time. It usually works on the uncertainty principle.
Applications of Quantum Mechanics
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Quantum mechanics is a branch of Physics whose applications are widespread in multiple domains, despite the fact that the discipline is still under research.
- It helps in developing various instruments in the information technology sector.
- Microsensors, quantum computers, imaging researchers, cryptography, etc are all made using advanced technology in Quantum Mechanics.
- Quantum mechanics form the basis for the evolution of the big bang theory.
- It also contributes to understanding the science behind the solar system, planets, stars, etc.
- The formation of semiconductors or microchips and lasers in the electrical and electronics industry also involves the usage of quantum mechanics.
- Quantum mechanics is also used in the healthcare sector in terms of its application in spectroscopy, MRIs, etc.
Facts About Quantum Mechanics
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Here are a few interesting facts about Quantum Mechanics:
- Quantum Mechanics exists everywhere around us. All things obey the laws of quantum mechanics.
- Quantum Mechanics is an area of active research.
- Multiple fields such as computers, thermodynamics, optics, meteorology, cryptography, etc have started the use of quantum mechanics.
- The theory of quantum mechanics is perfectly in sync with the theory of relativity. Hence, the information is never conveyed non-locally.
- Einstein didn’t deny the theory of quantum mechanics. He just pointed out that it was incomplete.
- Quantum Mechanics explains the reason why the quantum behavior of microscopic bodies is lost quickly due to the regular interactions the body has to go through.
- Hence, it can be said that Schrodinger’s Cat is either dead or it is alive. It surely can not be both.
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Things to Remember
- Quantum mechanics aims to understand the properties of matter with respect to its atomic and sub-atomic nature.
- Max Born, Wolfgang Pauli, and Werner Heisenberg coined the term ‘Quantum Mechanics’ in the early 1920s.
- Quantization, Quantum Entanglement, Uncertainty Principle, and Wave-particle Duality are the four sub-fields of Quantum Mechanics.
- Quantum mechanical model explains the electrons in terms of waves which is completely different from Bohr’s model.
- Quantum Mechanics was not completely denied by Einstein, rather, he believed that the theory was incomplete.
- It is an area of active research with the research being continued in various sub-fields.
Previous Year Questions
- The correct set of four quantum numbers for the outermost electron… (KCET 2012)
- The correct set of four quantum numbers for the valence electrons… (JEE Main 2013)
- Principal, azimuthal and magnetic quantum numbers are… (AIIMS 1999)
- The value of Planck's constant (h) is… (VITEEE 2017)
- With increasing principal quantum number, the energy difference…
- The following sets of quantum numbers represent four… (AIEEE 2012)
- Which quantum number is not related to the Schrodinger equation… (Rajasthan PMT 2002)
- Wave mechanical model of the atom depends upon…
- Dual behavior of matter was proposed by… (JKCET 2010)
- Though the quantum theory of light can explain a number of…
Sample Questions
Ques. What is Quantum Mechanics? (3 Marks)
Ans. Quantum mechanics is an evolving and advanced field of science that aims at understanding the properties of matter and objects in relation to the corresponding atomic and sub-atomic nature. It further illustrates the characteristics of the atoms, protons, electrons, neutrons, and gluons specifically and in the context of each other. It aims at studying electromagnetic radiation as well. Quantum Mechanics is a sub-part of the wider theory of Quantum Physics.
Ques. Define Quantum. Mention the four fields of Quantum Mechanics. (3 Marks)
Ans. Quantum refers to the minimum amount of the quantity of energy that lies under the direct proportion of the magnitude and the frequency along with its radiations.
The four fields of quantum mechanics are as follows.
- Quantization of Physical Properties
- Quantum Entanglement
- Uncertainty Principle
- Wave-particle Duality
Ques. Explain the two models of quantum mechanics. (3 Marks)
Ans. There are only two acceptable and working models of quantum mechanics. Both of them are as follows:
- Bohr Model is the first model which is currently accepted to understand Quantum Mechanics and its applications. The model is understood in terms of mathematics which can eventually explain complex structures.
- Quantum Mechanics Model is another acceptable model that founds its origin in quantum theory. It defines the exact properties of matter over a period of time and works on the uncertainty principle.
Ques. Describe the evolution of Quantum Mechanics. (3 Marks)
Ans. The research and theories on the discipline of Quantum Mechanics began in the 20th century, which was the same time Albert Einstein published his theory of relativity. The evolution of quantum mechanics cannot be attributed to a single scientist. It was a contribution of multiple scientists which gradually gained acceptance and verification for experiments in the late 1800s and 1930. The term “Quantum Mechanics” was eventually coined by a group of physicists namely Max Born, Wolfgang Pauli, and Werner Heisenberg in the early 1920s.
Ques. List the applications of Quantum Mechanics. (3 Marks)
Ans. The numerous applications of Quantum Mechanics are as follows:
- Various instruments such as quantum computers, microsensors, imaging researchers, etc. are developed using advanced techniques of Quantum Mechanics.
- The basis for the evolution of the big bang theory is backed by Quantum Mechanics.
- Quantum Mechanics is also used in the formation of semiconductors or microchips and lasers in the electrical industry.
Ques. Explain briefly the proposed model of Heisenberg for Quantum Mechanics. (1 Mark)
Ans. Heisenberg tried to explain quantum mechanics with respect to the actual property of electrons. He understood the actual property of electrons as a spinning matter and that too only in two directions, that is, either up or down.
Ques. Explain the relation between the microscopically small bodies and quantum mechanics. (2 Marks)
Ans. Quantum mechanics is the only branch of science that has successfully managed to explain the behavior of microscopic bodies. The theory found out the continuous interaction within the body is the reason why it loses its quantum rapidly. Thus, instilling a strong relationship between quantum mechanics and the microscopic bodies.
Ques. What is Electromagnetic Radiation? (3 Marks)
Ans. Electromagnetic Radiation is a form of energy that is produced by the movement of electrically charged particles traveling through a matter or vacuum or through oscillating magnetic and electric disturbance. It is a field in physics that refers to the waves of the electromagnetic field. The waves in the electromagnetic field propagate through space and carry electromagnetic radiant energy. There are several types of these waves such as microwaves, radio waves, visible light, X-rays, ultraviolet rays, and gamma rays.
Ques. Does Quantum Mechanics explain everything? (2 Marks)
Ans. Yes, Quantum Mechanics describes everything around us, whether we realize it or not. With the application of the power of quantum physics, several new technologies can be evolved, both for applications we use today and for those that may be available in the future.
Ques. Name the father of Quantum. (2 Marks)
Ans. Neil Bohr, Max Plank, and Albert Einstein are given the credit as the founding fathers of Quantum Theory. Neil Bohr and Max Plank were the recipients of the Nobel Prize for their work on Quanta. The evolution of quantum theory can be traced back to 1900 when German physicist Max Plank published the effect of radiation on a black body.
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