Section 1
History and Quantum Mechanical Quantities
By Boundless
![Thumbnail](../../../../../../figures.boundless-cdn.com/30674/raw/photoelectric-effect.jpg)
Electrons are emitted from matter that is absorbing energy from electromagnetic radiation, resulting in the photoelectric effect.
![Thumbnail](../../../../../../figures.boundless-cdn.com/11210/square/electromagnetic-spectrum.jpg)
The electromagnetic (EM) spectrum is the range of all possible frequencies of electromagnetic radiation.
![Thumbnail](../../../../../../figures.boundless-cdn.com/16908/square/military-laser-experiment.jpeg)
A photon is an elementary particle, the quantum of light, which carries momentum and energy.
![Thumbnail](../../../../../../figures.boundless-cdn.com/16912/square/rgb-laser.jpeg)
Quantum mechanics has had enormous success in explaining microscopic systems and has become a foundation of modern science and technology.
Wave–particle duality postulates that all physical entities exhibit both wave and particle properties.
![Thumbnail](../../../../../../figures.boundless-cdn.com/16907/square/difraccionelectronesmet.jpeg)
De Broglie's hypothesis was that particles should show wave-like properties such as diffraction or interference.
![Thumbnail](../../../../../../figures.boundless-cdn.com/16909/square/armonicoscillatoranimation.gif)
A wave function is a probability amplitude in quantum mechanics that describes the quantum state of a particle and how it behaves.
![Thumbnail](../../../../../../figures.boundless-cdn.com/17164/raw/davisson-germer-experiment.jpg)
The concept of "matter waves" or "de Broglie waves" reflects the wave-particle duality of matter.
![Thumbnail](../../../../../../figures.boundless-cdn.com/16910/square/heisenberg-microscope.jpg)
The uncertainty principle asserts a basic limit to the precision with which some physical properties of a particle can be known simultaneously.
![Thumbnail](../../../../../../figures.boundless-cdn.com/16911/square/bert-einstein-by-ehrenfest.jpeg)
Since its inception, many counter-intuitive aspects of quantum mechanics have provoked strong philosophical debates.