Quantum Mechanics

The 20^th Century saw many revolutions in physics and has been a very revolutionary century in science. In that year two theories were formulated that stand to be the pillars of physics to this day. The first one is the General Theory of Relativity and the other is Quantum Theory. The former was discovered independently by Albert Einstein in 1915 which is a theory of gravity which deals with the motions of planets and big celestial objects. The Quantum Theory is different from relativity. It deals with the micro-world, like properties of electrons, light quanta etc. both the theories are different form one another in their rules. One cannot use the laws of General Relativity in micro-world or the laws of Quantum Theory in macro-world. No such theory is still there that can explain both the worlds. The unification of these two theories is one of the greatest priorities of theoretical physics.

Now I will be sharing about Quantum Theory. Quantum Theory was originally started at the very beginning of the 20^th Century, in 1900 by Max Planck. He introduced the quantization of energy while solving the ultraviolet catastrophe. He said that energy is absorbed or emitted in small packets of energy called the quanta. This was the beginning of the quantum theory and for this explanation Max Planck got the Nobel Prize in 1918. The next phase of this theory was carried out by Albert Einstein. Albert Einstein in one of his paper in 1905 explained the phenomenon of photoelectric effect with Planck’s Quantum Theory. Here he showed that light is in fact composed of particles and each particle is a light-quanta or as later named as photon. Thus it was then concluded as that light has wave-particle duality. It shows both the wave like properties like interference and particle like properties like in the photoelectric effect. Then Louis de Broglie then proposed the wave-particle nature of matter also. He said that if light behaves like waves and particles then matter should also behave like wave and particle and discovered the wave nature of electrons. His theory led Erwin Schrodinger to develop a wave equation showing the wave like properties of matter. At the same time, Werner Heisenberg discovered his famous uncertainty principle which says that we cannot measure both the momentum and the position of an elementary particle (like an electron) simultaneously. Both Schrodinger and Heisenberg worked on and developed the foundations of the Quantum Mechanics. Later the quantum mechanics helped describe the model of the atom.

According to quantum mechanics we cannot say where an electron or any other such particle is, we can just define the mathematical probability of an electron to be found in such a place. In such a model this 3-Dimensional region, where the probability of finding an electron is maximum, is called an orbital. Thus if we beam a number of electrons in place we cannot say where any one of the electron will fall but we can calculate where is the maximum probability of finding the electron. The wave-particle nature of electron can be seen in the double-slit experiment. In this experiment, an electron is beamed from an emitter and there is a board in front having two holes through which the electron can pass. Now through which hole will this electron pass? Quantum mechanics say that the single electron will pass through both the holes and both have a probability of the electron to be passed. This may seem impossible but this is what is. The electron shows the wave like properties here. Every experiment performed to test quantum mechanics has proved quantum mechanics to be accurate.

Though Einstein laid foundations to this theory, he never accepted it’s non-deterministic nature. He said that “God does not play dice”.