# 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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