# How to understand quantum physics: 13 steps (with pictures)

Quantum physics (better known as quantum theory or quantum mechanics) is a branch of physics that gives a description of the behavior and interaction of matter and energy on the scale of subatomic particles, photons and certain materials at temperatures Very low. The quantum realm is defined as being where the "action" (or sometimes the angular momentum) of the particle is within a few orders of magnitude of a tiny physical constant called the Plank constant.

## Steps

### Step 1. You must understand the physical importance of Plank's constant

In quantum mechanics, the quantum action is Plank's constant, usually written as h. In the same way, for the interaction of subatomic particles, the quantum of the angular momentum is the reduced Plank constant (Plank's constant divided by 2π) written as ħ and called "bar h". Note that the value of Plank's constant is extremely small, that its units are those of angular momentum, and that the notion of action is the most general mathematical concept. As the name quantum mechanics implies, certain physical quantities such as angular momentum can change only in discrete quantities, and not continuously (cf. analogous). For example, the angular momentum of an electron attached to an atom or molecule is quantized and can only have values that are multiples of the reduced Planck constant. This quantization results in electron orbitals of a series of integers of the principal quantum number. In contrast, the angular momentum of an unbound electron is not quantized. Planck's constant also plays a role in the quantum theory of light, where the quantum of light is the photon and where matter and energy interact through the atomic electron transition or "jump" of the bonded electron. The units of Planck's constant can also be viewed as energy times time. For example, in the subject of particle physics, the notion of virtual particles are particles of great mass that appear spontaneously from a vacuum for a small fraction of a section and play a role in the interaction of the particles. The life limit of these virtual particles is the energy (mass) of the particle for that lifetime. Quantum mechanics is a big topic, but every part of your math involves Planck's constant.

### Step 2. Keep in mind that high-mass particles go through a classical to quantum transition

Although the free electron shows some quantum properties (such as spin), as the unbound electron approaches the atom, it slows down (perhaps due to light-emitting photons), and undergoes a transition from classical to normal behavior. quantum while its energy falls below ionization energy. The electron binds the atom and its angular momentum with respect to the atomic nucleus is limited to the quantized values of the orbitals it can occupy. The transition is sudden. One could compare this transition to that of a mechanical system changing from unstable display to stable behavior or from simple display to chaotic behavior, or even a decelerating rocket going below escape velocity and into orbit. around a star or other celestial object. In contrast, photons (which are massless) do not go through that transition: photons only travel through space unchanged until they interact with other particles and then disappear. Looking up into the night sky, some star's photons traveled through light years of space unchanged and then interacted with an electron in a molecule on your retina, transferred its energy, and then disappeared.

### Step 3. These are some of the new ideas presented in quantum theory:

1. The quantum realm follows very different rules than the everyday world we experience.
2. The action (or angular momentum) is not continuous, but comes in small but discrete units.
3. Elementary particles behave like particles and like waves.
4. The motion of a specific particle is inherently random and can only be predicted in terms of probabilities.
5. It is physically impossible to simultaneously measure the position and momentum of a particle beyond the precision allowed by Planck's constant. The more accurate is known, and the measurement of the other is less accurate.

### Step 4. Understand what particles and wave duality are

It postulates that all matter has both wave and particle properties. A central concept of quantum mechanics, this duality refers to the inability of classical concepts like "particle" and "wave" to fully describe the behavior of objects on a quantum scale. For a complete understanding of the duality of matter, one must have concepts of the Compton effect, photoelectric effect, de Broglie wavelength, and Planck's formula for black body radiation. All these effects and theories demonstrate the dual nature of matter. There are different experiments for light by scientists that show that light has a dual nature, that is to say particles, as well as wave nature … In 1901, Max Planck published an analysis that managed to reproduce the observed spectrum of light emitted by an object shiny. To achieve this, Planck had to make an ad hoc mathematical assumption of quantized action of the oscillators (black body atoms) that emit radiation. It was Einstein who later proposed that it is electromagnetic radiation itself that is quantized into photons.

### Step 5. Understand the uncertainty principle

The uncertainty principle states that certain pairs of physical properties, such as position and moment, cannot be known simultaneously to arbitrarily high precision. In quantum physics, a particle is described as a wave packet, which gives rise to this phenomenon. Consider measuring the position of a particle. It could be anywhere. The particle's wave packet has a non-zero amplitude, that is, the position is uncertain, it could be anywhere along the wave packet. To get an accurate position reading, this wave packet must be "compressed" as much as possible, which means it must be made up of increasing numbers of sine waves that are close together. The momentum of the particle is proportional to the wave number of one of these waves, but it could be any of them. So a more precise position measurement, by adding more waves, means that the moment measurement becomes less precise (and vice versa).

### Step 6. Understand the wave function

A wave function or wave function is a mathematical tool of quantum mechanics, which describes the quantum state of a particle or system of particles. It is commonly applied as a property of particles in relation to their wave-particle duality, where ψ (position, time) is denoted and where | ψ |2 is equal to the probability of finding the object at a given time and position. For example, in an atom with a single electron, such as ionized hydrogen or helium, the electron wave function provides a complete description of how the electron behaves. It can be decomposed into a series of atomic orbitals that form a basis for the possible wave functions. For atoms with more than one electron (or any system with multiple particles), the underlying space is the possible configurations of all electrons and the wave function describes the probabilities of those configurations. In solving homework problems involving the wave function, familiarity with complex numbers is a prerequisite. Other requirements include linear algebra calculations, Euler's formula for complex analysis, and bra-ket notation.

### Step 7. Understand the Schrödinger equation

It is an equation that describes how the quantum state of a physical system changes over time. It is a central element of quantum mechanics just as Newton's laws are for classical mechanics. Solutions to the Schrödinger equation describe not only molecular, atomic, and subatomic systems, but also macroscopic systems, possibly even the entire universe. The most general form is the time-dependent Schrödinger equation which gives a description of a system evolving with time. For systems in a steady state, the time-independent Schrödinger equation is sufficient. Approximate solutions independent of time. The Schrödinger equation is commonly used to calculate energy levels and other properties of atoms and molecules.