What Does Quantum Means?
Quantum means a definite amount. Light, heat and X-rays are forms of energy. All energy may be thought of as small amounts or packets of energy called quanta (the plural of quantum). So, a light ray becomes not a long stream of light, but many tiny quanta. A quantum of light is called photon. This way of thinking is known as the quantum theory. It was put forward by Max Planck in 1901, and has been used by other scientists to explain the structure of the atom.
Max Planck used quanta to mean “quanta of matter and electricity”, gas, and heat. In 1905, in response to Planck’s work and the experimental work of Lenard (who explained his results by using the term quanta of electricity), Albert Einstein suggested that radiation existed in spatially localized packets which he called “quanta of light” (“Lichtquanta”).
The word quantum comes from the Latin quantus, meaning “how great”. “Quanta”, short for “quanta of electricity” (electrons), was used in a 1902 article on the photoelectric effect by Philipp Lenard, who credited Hermann von Helmholtz for using the word in the area of electricity. However, the word quantum in general was well known before 1900.
It was often used by physicians, such as in the term quantum satis. Both Helmholtz and Julius von Mayer were physicians as well as physicists. Helmholtz used quantum with reference to heat in his article on Mayer’s work, and the word quantum can be found in the formulation of the first law of thermodynamics by Mayer in his letter dated July 24, 1841.