positron
Positrons are the anti-particles of electrons: light elementary particles with positive electric
polarization
Waves that are especially simple can be completely described by stating the direction in which they propagate, their speed of propagation, frequency, and amplitude. But there are also simple waves where these quantities are not sufficient for a complete ...
point
Elementary "building block" of geometrical entities such as surfaces or more general spaces. For instance, a surface is the set of all its points, of all possible locations on the surface, and all geometrical objects in that surface are defined by the points ...
plasma
State of matter in which the atoms are largely or even completely separated into electrons and atomic nuclei, which fly around in a highly energetic mixture. Compare the other states of matter: solid state, gas, ...
planet
Planets are not-too-small companions of a star that are not stars themselves (nor ever were stars). In our solar system, the planets are, listed from the one closest to the sun to the one farthest: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, ...
plane
A surface within which the axioms of Euclidean geometry (synonym: plane geometry) hold - the rules of geometry as they are taught in high school, with well-known formulae such as Pythagoras's theorem and "the perimeter of a circle is 2 times pi times its ...
Planck’s radiation law
The fundamental law governing the properties of the simplest form of thermal radiation - that emitted by a blackbody. It describes the spectrum of such radiation in terms of universal constants and a single parameter - the body's temperature. ...
Planck’s constant
Fundamental constant of quantum theory; of the dimension energy times time. For instance, the energy of a single photon is equal to Planck's constant times the photon's frequency. Abbreviated as h in ...
