group velocity of light
61Galileo Galilei — For other uses of Galileo , see Galileo (disambiguation). For other uses of Galileo Galilei , see Galileo Galilei (disambiguation) …
62Biquaternion — In abstract algebra, the biquaternions are the numbers where w, x, y, and z are complex numbers and the elements of {1, i, j, k} multiply as in the quaternion group. As there are three types of complex number, so there are three types of… …
63parallax — parallactic /par euh lak tik/, adj. parallactically, adv. /par euh laks /, n. 1. the apparent displacement of an observed object due to a change in the position of the observer. 2. Astron. the apparent angular displacement of a celestial body due …
64Matter wave — This article is about the quantum mechanical concept of all matter having a duality model as a wave. For the ordinary type of wave propagating through material media, see Mechanical wave. In quantum mechanics, a matter wave or de Broglie wave (… …
65Photon — This article is about the elementary particle of light. For other uses, see Photon (disambiguation). Photon Photons emitted in a coherent beam from a laser Composition Elementary particle …
66Ultrashort pulse — In optics, an ultrashort pulse of light is an electromagnetic pulse whose time duration is on the order of the femtosecond (10 − 15 second). Such pulses have a broadband optical spectrum, and can be created by mode locked oscillators. They are… …
67radioactivity — /ray dee oh ak tiv i tee/, n. Physics, Chem. the phenomenon, exhibited by and being a property of certain elements, of spontaneously emitting radiation resulting from changes in the nuclei of atoms of the element. Also called activity. [1895… …
68Optical parametric amplifier — An optical parametric amplifier, abbreviated OPA, is a laser light source that emits light of variable wavelengths by an optical parametric amplification process. Contents 1 Optical parametric generation (OPG) 2 Optical parametric amplification… …
69transuranium element — Any of the chemical elements after uranium in the periodic table (with atomic numbers greater than 92). All are radioactive (see radioactivity), with half lives ranging from tens of millions of years to fractions of a millisecond. Only two,… …
70Nanotube nanomotor — A device generating linear or rotational motion using carbon nanotube(s) as the primary component, is termed a nanotube nanomotor. Nature already has some of the most efficient and powerful kinds of nanomotors. Some of these natural biological… …
