By the 1890s most scientists thought light moved in waves.
Max Planck (1858-1947) realized that the range of radiation given out by a hot object is not quite what scientists would calculate it to be if radiation is waves.
Planck realized that the radiation from a hot object could be explained if the radiation came in chunks, or quanta.
Quanta are very, very small. When lots of quanta are emitted together they appear to be like smooth waves.
In 1905 Einstein showed that quanta explain the photoelectric effect.
In 1913 Niels Bohr showed how the arrangement of electrons in energy levels around an atom (see electrons) could be thought of in a quantum way too.
In the 1920s Erwin Schrodinger and Werner Heisenberg developed Bohr’s idea into quantum physics, a new branch of physics for particles on the scale of atoms. 200
Quantum physics shows how radiation from a hot object is emitted in little chunks that are called quanta.
Quantum physics explains how electrons emit radiation (see above). It shows that an electron is both a particle and a wave, depending on how you look at it. It seems to work for all four fundamental forces (see forces) except gravity.
The development of the technologies that gave us lasers and transistors came from quantum physics.
Quantum physics predicts some strange things on the scale of atoms, such as particles appearing from nowhere and electrons.