In the last article, we have learnt the closest theory to the theory of everything, which is “String Theory.” In this article, let us try to understand Quantum physics.

Quantum Physics: Quantum physics is the study of matter and energy at its most fundamental level. The basic story of everything around us and including us are elementary particles. So in simple terms, quantum physics is the study of everything in the universe. It explains how everything works in the universe.

Pictorial representation of quantum physics.

Quantum physics and quantum mechanics are similar; the term “mechanics” indicates doing calculations. So how did the idea of quantum mechanics come to existence? To understand that we should know the concepts of electromagnetism. 

Electromagnetism: At the subatomic level, electromagnetism is defined as the force between electrically charged particles. It is the fundamental reason electrons bound to the nucleus and responsible for the complete structure of the atom.

Electromagnetic force: It is is a type of physical interaction that occurs between electrically charged particles. It acts between charged particles and is the combination of all magnetic and electrical forces. It can be attractive or repulsive.

Electromagnetic waves: These are the waves generated when an electric field comes in contact with the magnetic field. These are the combination of oscillating electric and magnetic fields.

In 1900, a group of bulb manufacturers came to Max Planck to know how to make their bulbs more efficient and take less electricity. He conducted a few experiments and was shocked by the results. According to classical laws of physics, the energy emitted by a body is continuous, but when he observed the energy emitted by the light bulbs, it was discrete. So the basis of all quantum physics, the “Planck’s Law” was born.

Black Body:   A blackbody is an object that absorbs all the radiation falling on it. An object that absorbs all the radiation can also emit all radiation. Therefore, a blackbody will radiate maximum energy when heated to a given temperature. The energy was not continuous, so Planck came up with the “Planks Quantum Theory” Or “Planck’s Law.”

Black body graph.

Planck’s Quantum Theory: Planks Quantum Theory says that energy of electromagnetic radiation is transferred in terms of energy bundles, these bundles are called “Quantum” or “Quanta” can also be called as “Photons.” The energy of each photon is directly proportional to the frequency of electromagnetic radiation.

It was a revolution in the field of physics, Planck got Nobel prize for the same in 1918. However, this theory was limited to the black body. In 1913 “Niels Bohr” came up with his atomic model which paved the way for quantum theory to the atomic level. According to his atomic model, energy is transferred only in specific, well-defined quantities. Electrons should move around the nucleus but only in prescribed orbits. When jumping from one orbit to another with lower energy, a light quantum is emitted. Bohr’s theory could explain why atoms emitted light in fixed wavelengths. The modern shape of quantum physics was given by “Albert Einstein” with his “Photo-Electric Effect.”

Photo Electric Effect:  It is a phenomenon in which, electrons are emitted from a metal surface when light is incident on it. In physics terms, electrically charged particles are discharged from or within a material when it absorbs electromagnetic radiation. In this, Einstein used the principle of packet energy called quanta and proved the quantum physics existence on materials absorbing light.

Pictorial representation of photo electric effect.

The phenomena of Quantum Physics:

Wave-Particle Duality: Imagine subatomic particles as balls bouncing around, but sometimes we have to imagine them as spread-out waves and now consider them doing both, yes it is a bit hard to imagine. Try painting this picture. You took a subatomic particle and increased its sizes to that of a stone. You have thrown that into a small water body. What do we observe? Ripples on the surface, which are nothing but waves. Now Imagine one of the waves has hit a stick on the way, and all the waves disappear. Now your stone sized subatomic particle pops up from that the point of the stick. It is strange, but yeah that is how subatomic particles exhibit the properties of a wave and a particle. 

Pictorial representation of wave-particle duality.

Quantum Tunneling: Now imagine you have a football and kicking it against the wall, it keeps coming back, and you continue this for some time. Suddenly, the football without smashing or interacting with the wall passed through the wall and came out on the other side and moving away. Yes, this crazy! But this is what happens at the subatomic level. Quantum tunnelling is an important reason why we exist. Inside the sun as we know emits light by nuclear fusion in which two hydrogen atoms come together, and the protons in their nucleus will bounce off each other. If there were no quantum tunnelling, even the nuclei and the hydrogen atoms would bounce of each other, and there would be nuclear fusion. For fusion to happen, they quantum tunnel through each other, giving us the sunlight and without sunlight, there is no existence of life form. 

Pictorial representation of quantum tunneling.

Superposition: Imagine a ballet dancer doing a pirouette, yeah it is lovely same is quantum physics, now imagine a ballet dancer doing an anti-clock pirouette, yes it is hard now comes the fun part. Imagine a ballet dancer doing the clockwise and anti-clockwise pirouettes at the same time. Yes, it is tough to imagine, but that is the concept of superposition. When we got to get a scan under the MRI machine, the machine turns the hydrogen atoms in our body in both ways so that the doctors can see inside the body. 

Pictorial Representation of Super position.

It is tough to imagine these like two spins at the same time, tunnelling etc., But we can describe it properly using mathematics. The applications of quantum physics are very vast and very useful. As said above the MRI machine is one of them. By understanding the properties of silicon, we designed silicon chips which are the building blocks of computers and its technology. Not only these but they helped us build x rays, lasers, holography, the modern-day periodic table, fluorescence materials and many more important technologies that we see today. 

In short, without the understanding and usage of quantum physics, we would never be living this lifestyle, and we would be backward by at least 100 years. 


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