# An Easy Explanation of the Basics of Quantum Mechanics for Dummies

Next time when a physics professor says that the probability of your position at any given time, in the whole universe, is never zero, don't think he has lost his marbles. This is where we can start with an explanation of the basics of quantum mechanics for dummies.

Swapnil Srivastava

Last Updated: Feb 3, 2018

**. Richard Feynman, one of the founders of quantum field theory remarked,**

*"Anyone who is not shocked by quantum theory has not understood it"***.**

*"I think I can safely say that nobody understands quantum theory"*Introduction to Quantum Mechanics

Black Body Radiation

*any object capable of absorbing radiation at all frequencies and radiating it back*) would emit infinite amount of energy. This was not found to be true experimentally. The energy emitted by a black body seemed to be a function of its frequency, showing a typical bell shaped curve. In 1901, Max Planck accurately described the energy output of a black body, by introducing the Planck's constant (

**h = 6.626068 x 10-34 m2 kg/s**).

**E = hν**

*where E is energy, h is the Planck's constant and ν is the frequency of radiation*), implied that energy could only be traded in '

*packets*' or '

*quanta*'. This discretization brought in by energy quanta was a fundamental shift in thinking, inconsistent with classical institution of physicists at the time. That's why the theory came to be known as

*quantum physics*.

The Photoelectric Effect

*photons*, successfully explaining the photoelectric effect in terms of light frequency. Thus light, which was hitherto known to be a wave, was now known to have a dual character - that of a

*wave*and a

*particle*.

Optical Line Spectra

Basics of Quantum Physics For Dummies

De Broglie's Matter Waves

*Matter Waves*corresponding to every particle, whose wavelength would be inversely proportional to the momentum of the particle.

**λmatter = h / p**

(

*where h is the Planck's constant and p is the momentum*)

In 1926, Erwin Schrödinger formulated an equation that described the behavior of these matter waves. He successfully derived the energy spectrum of Hydrogen atom, by treating orbital electrons as standing matter waves. Max Born interpreted the square of amplitude of these waves to be the

*probability*of finding associated particles in a localized region. All these developments led to the establishment of quantum mechanics as a scientific theory, well grounded in experiment and formalism. The wavefunction describing any particle in quantum mechanics is a matter wave, whose form is computed through the use of Schrödinger equation. Ergo, matter waves form the central most important feature of quantum mechanics.

Heisenberg's Uncertainty Principle

**. - Werner Heisenberg**

*The more precisely the position is determined, the less precisely the momentum is known in this instant, and vice versa***Δx.Δp ≥ h/2π**

(

*where Δx is the uncertainty in position, Δp is the uncertainty in momentum and h is Planck's constant*)

*matter wave*, is inherently delocalized (

*spread out in space*). The more accurately you know the position, more uncertain you are about the momentum and vice versa. Generally, the uncertainty principle is applicable to any dual set of complementary physical quantities that cannot be measured with arbitrary precision.

The Wavefunction (Ψ) Encodes All Particle Information

*fixed*orbit or

*trajectory*goes for a toss. You can no longer plot the path of a particle on a graph, like in Newtonian mechanics.

*a partial differential equation that can determine the nature and time development of the wavefunction*.

Determinism is Probabilistic

*the wave function*) - for a system, the probability of a particle's position is determined by the square of its modulus - │Ψ│2.

**So we have**.

*essentially given up on predicting the position of a particle accurately, because of the uncertainty principle. All we can do is predict the probabilities*Schrödinger's Cat in a Box

*the cat is both dead and alive*! This is the fundamental paradox presented by the theory. It's one way of illustrating the way quantum mechanics forces us to think. Until the position of a particle is measured, it exists in all positions at the same time, just like the cat is both dead and alive.

*the phenomenon known as quantum entanglement*), frictionless fluid flow in the form of superfluids with zero viscosity and current flow with zero resistance in superconductors. It may one day revolutionize the way computers operate, through quantum computing. It also lays the foundation of advanced theory of relativity, knows as quantum field theory, which underlies all of particle physics.

At the initial stage, you might find your brain circuits getting fused, while trying to grasp the basics of quantum mechanics. However, as you delve deeper into quantum wonderland, into the intricacies and complexities of equations and see the application in real life, the fascination goes on rising, revealing beauty at the most fundamental level. The world is not just what is seen by naked eyes, but something which is far beyond our comprehension. Quantum mechanics has revolutionized the study of physics, and opened the gateway to see new horizons.