symmetric wave
51optics — /op tiks/, n. (used with a sing. v.) the branch of physical science that deals with the properties and phenomena of both visible and invisible light and with vision. [1605 15; < ML optica < Gk optiká, n. use of neut. pl. of OPTIKÓS; see OPTIC,… …
52physical science — physical scientist. 1. any of the natural sciences dealing with inanimate matter or with energy, as physics, chemistry, and astronomy. 2. these sciences collectively. [1835 45] * * * Introduction the systematic study of the inorganic world …
53syndrome — The aggregate of symptoms and signs associated with any morbid process, and constituting together the picture of the disease. SEE ALSO: disease. [G. s., a running together, tumultuous concourse; (in med.) a concurrence of symptoms, fr. syn,… …
54Mathematics of radio engineering — A complex valued function. The mathematics of radio engineering is a pleasant and very useful subject. This article is an attempt to provide a reasonably comprehensive summary of this almost limitless topic. While the ideas have historically… …
55Musical acoustics — or music acoustics is the branch of acoustics concerned with researching and describing the physics of music – how sounds employed as music work. Examples of areas of study are the function of musical instruments, the human voice (the physics of… …
56Electrovacuum solution — In general relativity, an electrovacuum solution (electrovacuum) is an exact solution of the Einstein field equation in which the only nongravitational mass energy present is the field energy of an electromagnetic field, which must satisfy the… …
57Wheeler–Feynman absorber theory — The Wheeler–Feynman absorber theory is an interpretation of electrodynamics that starts from the idea that a solution to the electromagnetic field equations has to be symmetric with respect to time inversion, as are the field equations themselves …
58Entropy (arrow of time) — Entropy is the only quantity in the physical sciences that picks a particular direction for time, sometimes called an arrow of time. As one goes forward in time, the second law of thermodynamics says that the entropy of an isolated system can… …
59Vibrations of a circular drum — [ drum (mode u {12} with the notation below). Other modes are shown at the bottom of the article.] The vibrations of an idealized circular drum, essentially an elastic membrane of uniform thickness attached to a rigid circular frame, are… …
60cosmos — /koz meuhs, mohs/, n., pl. cosmos, cosmoses for 2, 4. 1. the world or universe regarded as an orderly, harmonious system. 2. a complete, orderly, harmonious system. 3. order; harmony. 4. any composite plant of the genus Cosmos, of tropical… …
