# quantum theory

## Definitions

### Astronomy

- Theory developed by Danish physicist Neils Bohr (1885–1962) which states that at the smallest scale, energy exists in discontinuous ‘lumps’ or quanta rather than being infinitely divisible. Thus lines in the spectra of stars mark the quantum of energy separating two different energy levels of a particular electron in an atom, the energy of the transition being given by h, Planck’s constant, multiplied by the frequency of the spectral line.

### Electronics

- The
__theory__ according to which __energy__ is emitted or absorbed in __discrete__ units called __quanta__. It describes the behavior of atomic and subatomic particles and systems. According to quantum theory, electromagnetic radiation has both particle-like properties, as seen in the photoelectric effect, and wavelike properties, as evidenced by __phenomena__ such as diffraction and interference. Such __radiation__ is composed of photons, whose energy is equal to *hf*, where *h* is the __Planck constant__, and *f* is the frequency of the radiation in __hertz__. Also called quantum mechanics (2). - synonymquantum mechanics

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