What is the Quantum Physics ?

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Quantum theory is the theoretical basis of modern physics that explains the nature and behavior of matter and energy on the atomic and subatomic level. The nature and behavior of matter and energy at that level is sometimes referred to as quantum physics and quantum mechanics.

In 1900, physicist Max Planck presented his quantum theory to the German Physical Society. Planck had sought to discover the reason that radiation from a glowing body changes in color from red, to orange, and, finally, to blue as its temperature rises.

He found that by making the assumption that energy existed in individual units in the same way that matter does, rather than just as a constant electromagnetic wave - as had been formerly assumed - and was therefore quantifiable, he could find the answer to his question.

Planck wrote a mathematical equation involving a figure to represent these individual units of energy, which he called quanta.

The equation explained the phenomenon very well; Planck found that at certain discrete temperature levels (exact multiples of a basic minimum value), energy from a glowing body will occupy different areas of the color spectrum.

Planck assumed there was a theory yet to emerge from the discovery of quanta, but, in fact, their very existence implied a completely new and fundamental understanding of the laws of nature. Planck won the Nobel Prize in Physics for his theory in 1918, but developments by various scientists over a thirty-year period all contributed to the modern understanding of quantum theory.

In 1900, Planck made the assumption that energy was made of individual units, or quanta.

In 1900, Planck made the assumption that energy was made of individual units, or quanta.

In 1924, Louis de Broglie proposed that there is no fundamental difference in the makeup and behavior of energy and matter; on the atomic and subatomic level either may behave as if made of either particles or waves. This theory became known as the principle of wave-particle duality: elementary particles of both energy and matter behave, depending on the conditions, like either particles or waves.

Quantum physics is necessary to understand the properties of solids, atoms, nuclei, subnuclear particles and light. In order to understand these natural phenomena, quantum principles have required fundamental changes in how humans view nature.

the conflict between the fundamental probabilistic features of quantum mechanics and older assumptions about determinism provided a cognitive shock that was even more unsettling that the revised views of space and time brought by special relativity.

The word quantum refers to discreteness, i.e., the existence of individual "lumps" as opposed to a continuum. In Newtonian physics, all quantities are allowed to be continuous. For instance, particles can have any momentum and light can have any frequency. A quantum is a discrete packet of energy, charge, or any other quantity. For instance, one might say that electric charge is quantized in units of e=1.602e-19 C.

In the next few pages, we will discuss the fact that all exchanges of energy come in discrete amounts. For instance, when light is absorbed by some material, the energy of the material does not rise continuously, but in discrete jumps. Each jump occurs when the material absorbs a single quantum of light.

We will also learn that energy levels ("orbits") of an electron in an atom do not have a continuous range of possible energies, but instead that only discrete "orbits" are possible.

This strange behavior is linked to the concept of wave-particle duality. We will see that particles can be described by wave functions that tell the probability of finding the particle.

Quantum physics is necessary to understand the properties of solids, atoms, nuclei, subnuclear particles and light. In order to understand these natural phenomena, quantum principles have required fundamental changes in how humans view nature.

To many philosophers (Einstein included), the conflict between the fundamental probabilistic features of quantum mechanics and older assumptions about determinism provided a cognitive shock that was even more unsettling that the revised views of space and time brought by special relativity.

The word quantum refers to discreteness, i.e., the existence of individual "lumps" as opposed to a continuum. In Newtonian physics, all quantities are allowed to be continuous.

In the next few pages, we will discuss the fact that all exchanges of energy come in discrete amounts. For instance, when light is absorbed by some material, the energy of the material does not rise continuously, but in discrete jumps.

Each jump occurs when the material absorbs a single quantum of light. We will also learn that energy levels ("orbits") of an electron in an atom do not have a continuous range of possible energies, but instead that only discrete "orbits" are possible

This strange behavior is linked to the concept of wave-particle duality. We will see that particles can be described by wave functions that tell the probability of finding the particle.

Quantum theory is one of the most successful theories in the history of physics. The accuracy of its predictions is astounding. The breath of its application is impressive

Quantum theory is used to explain how atoms behave, how elements can combine to form molecules, how light behaves, and even how black holes behave. There can be no doubt that there is something very right about quantum theory.

But at the same time, it is difficult to understand what quantum theory is really saying about the world. In fact, it is not clear that quantum theory gives any consistent picture of what the physical world is like.