extremely high frequencies
51Schumann resonances — The Schumann resonances (SR) are a set of spectrum peaks in the extremely low frequency (ELF) portion of the Earth s electromagnetic field spectrum. Schumann resonances are global electromagnetic resonances, excited by lightning discharges in the …
52Crystal — /kris tl/, n. 1. a city in SE Minnesota, near Minneapolis. 25,543. 2. a female given name. * * * I Any solid material whose atoms are arranged in a definite pattern and whose surface regularity reflects its internal symmetry. Each of a crystal s… …
53Mechanical filter — Figure 1. A mechanical filter made by the Kokusai Electric Company intended for selecting the narrow 2 kHz bandwidth signals in SSB radio receivers. It operates at 455 kHz, a common IF for these receivers, and is dimensioned 45×15×15 mm ( …
54Test probe — Typical passive oscilloscope probe being used for testing an integrated circuit. A test probe (test lead, test prod, or scope probe) is a physical device used to connect electronic test equipment to the device under test (DUT). They range from… …
55Line array — The term line array means a speaker system that is made up of a varying number of vertically arranged units which give the effect of a single sound source with the same dimensions as the total of the unit of which is made up, the performance of… …
56bat — bat1 /bat/, n., v., batted, batting. n. 1. Sports. a. the wooden club used in certain games, as baseball and cricket, to strike the ball. b. a racket, esp. one used in badminton or table tennis. c. a whip used by a jockey. d. the act of using a… …
57nebula — nebular, adj. /neb yeuh leuh/, n., pl. nebulae / lee , luy /, nebulas. 1. Astron. a. Also called diffuse nebula. a cloud of interstellar gas and dust. Cf. dark nebula, emission nebula, reflection nebula …
58laser — /lay zeuhr/, n. Physics. a device that produces a nearly parallel, nearly monochromatic, and coherent beam of light by exciting atoms to a higher energy level and causing them to radiate their energy in phase. Also called optical maser. [1955 60; …
59ultrasonics — /ul treuh son iks/, n. (used with a sing. v.) the branch of science that deals with the effects of sound waves above human perception. [1930 35; see ULTRASONIC, ICS] * * * Vibrational or stress waves in elastic media that have a frequency above… …
60Sonar — This article is about underwater sound propagation. For atmospheric sounding, see SODAR. For other uses, see Sonar (disambiguation) …
