## QUANTUM MECHANICS

This site is mainly intended for high school students and discussing Quantum Mechanics here, with all its intricacies and delicacies is out of question. The complicated Mathematics required by Quantum Mechanics traditionally reserves it for higher classes, for those students who have had taken courses in Advanced Mathematics. But I think some junior students are interested in this subject and this article is intended for them. Here I've attempted to give a brief introduction to Quantum Mechanics without the use of any Mathematics.

Quantum Mechanics is that branch of Physics which is concerned with the study of light, matter and the interaction of the two at an extremely small scale - the atomic scale. No one man can be credited with the development of this theory and also the dates can’t be fixed with accuracy. Roughly it may be said that the work on this theory began with the start of twentieth century by Max Planck with the explanation of the puzzle of black body radiation and was completed in 1927 by Werner Heisenberg with the discovery of his famous uncertainty principle.

When some entity occurs in only discrete values we say it is quantized and the difference between two consecutive values is called the quantum. For example the number of students in a school is quantized because the number of students can only be an integer. There can be no 976.3 students in a school. Hence the number of students is quantized and its quantum is 1.

In Quantum Mechanics many physical quantities [like energy, momentum] which were not thought to be quantized before this theory was given; were found to be quantized and hence the name. But this quantization or any other result of Quantum Mechanics is observed properly in only the atomic world or the microscopic world. In the large sized world or the macroscopic world the results of Quantum Mechanics merge into the results of Classical Mechanics hence there is no need of applying Quantum Mechanics in every day world.

Quantum Mechanics introduces one to a world which is totally bizarre and new to him and I am afraid I can’t explain it with any analogies. Things at the atomic scale do not behave like any other thing that you know of. An electron (say) can sometimes behave like a particle and sometimes as a wave. Sometimes it seems it is occupying two positions simultaneously! In fact even the experts of this field do not understand it the way they would like to. Neil’s Bohr, one of the originators of Quantum Mechanics remarked; “If you think you are not confused by Quantum Physics then you haven’t really understood it.”

Einstein never accepted this theory. He said; “I can never believe that God is playing dice with us.” This famous remark was his way to disagree with the Heisenberg’s uncertainty principle. This principle is one of the basic postulates of Quantum Mechanics.

In one form, the uncertainty principle says that it is impossible to determine the exact position and exact speed of a particle simultaneously. This postulate is directly contradicting the old Newtonian or classical view of Nature which allowed such calculations. Actually before the uncertainty principle the indeterminacy in calculations was due to incapabilities of the measuring instrument but Heisenberg was arguing otherwise. He claimed that we cannot know the two parameters of a particle not because our means are limited but because Nature itself doesn’t possess them! This makes no sense but its indeed true.

The whole theory of Quantum Mechanics is contained in one differential equation given by Erwin Schrodinger. Even in its most simplest forms; its extremely difficult to solve but if solved – it reveals whatever you wish to know about Nature as far as She permits you to know.

Quantum Mechanics is the only completely successful theory of the microscopic world. It was due to Quantum Mechanics that we got equipments like calculators, computers, TV remotes etc.

Quantum Mechanics has survived every experimental test devised so far. There are some physicists who are still working to disapprove this theory but no one has succeeded. (Yet?)