The fundamental theory of physics describing nature at the smallest scales, involving wave-particle duality and quantization.Quantum mechanics is the fundamental theory of physics that describes nature at atomic and subatomic scales. It replaces the deterministic, continuous world of classical physics with a probabilistic, discrete one: energy comes in quantized packets, particles exhibit wave-particle duality, and measurement itself affects the system. It explains everything from the stability of atoms to the behavior of semiconductors, and it underpins modern chemistry and electronics.
Quantum mechanics was developed in the 1920s by a cohort including Max Planck, Albert Einstein, Niels Bohr, Werner Heisenberg, Erwin Schrödinger, and Paul Dirac, building on Planck's 1900 quantum hypothesis.
The theory is built on a few core principles. First, a quantum system is described by a wavefunction, which encodes the probabilities of finding the system in various states. Second, observable quantities like energy or momentum are quantized—they can only take certain discrete values. Third, the act of measurement 'collapses' the wavefunction to a definite outcome, a process that remains deeply mysterious. Mathematically, the Schrödinger equation governs how wavefunctions evolve in time, and the Heisenberg uncertainty principle sets fundamental limits on simultaneous measurements.
It is the basis for all modern electronics—transistors, lasers, LEDs, MRI scanners—and for emerging technologies like quantum computing and quantum cryptography.
The famous 'double-slit' experiment, where single electrons create interference patterns, demonstrates that particles behave as waves until observed—a result that still has no classical explanation.



