Quantum Mechanics is a set of physical theories that emerged in the twentieth century to explain phenomena at the atomic and subatomic levels. It merged the properties of particles and waves, giving rise to the term wave-particle duality. Consequently, quantum mechanics is responsible for the physical interpretation at the atomic level and also applies to classical mechanics, though its effects are not apparent at that scale. Therefore, quantum mechanics is a generalization of classical physics, applicable to both the atomic and macroscopic levels.

Its naming as quantum mechanics stems from the importance of the 'quantum' in its foundation—a physical term used to describe the smallest amount of energy that can be exchanged between particles. It refers to the discrete, not continuous, quantities of energy that are emitted.

The terms 'quantum physics' and 'quantum theory' are often used as synonyms for quantum mechanics. Some writers use the term 'quantum mechanics' to refer specifically to non-relativistic quantum mechanics.

Contradictions in the classical physics' conception of the atom at the time: In the early twentieth century, the atom was imagined to be like a miniature solar system, with the nucleus at the center and electrons orbiting it. However, according to the principles of classical physics, the electrons in this model would experience centripetal acceleration, causing them to emit electromagnetic radiation. This would lead to a gradual loss of energy, causing them to spiral into the nucleus in a fraction of a second. This necessitated a new theory to provide a different model for atomic structure.

Classical theory also posited that atomic spectra should cover all wavelengths with equal intensity. However, physicists observed that experimental results starkly contradicted this, as different atoms emit spectra (light waves) at very specific, discrete wavelengths.

Another problem arose with the 'black body' paradox—an object that absorbs all incident radiation and then re-emits it completely. All attempts based on traditional statistical physics failed to explain the black-body radiation curve, especially at high frequencies, a failure that became known as the 'ultraviolet catastrophe.' It became clear that the laws of thermodynamics were insufficient to explain this phenomenon.

• Weight: 0.72 kg
• Dimensions: 17 × 24 cm
• ISBN: 978-9957-126-62-9