Columbia Encyclopedia

Search results

500 results found

bromide

(Encyclopedia)bromide, any of a group of compounds that contain bromine and a more electropositive element or radical. Bromides are formed by the reaction of bromine or a bromide with another substance; they are wi...

halo, in meteorology

(Encyclopedia)halo, in meteorology, short-lived circles or arcs, and less commonly spikes and crosses, of colored or whitish light surrounding the moon or sun or in clouds as seen from above. A halo occurs when the...

tropism

(Encyclopedia)tropism trōpˈĭzəm [key], involuntary response of an organism, or part of an organism, involving orientation toward (positive tropism) or away from (negative tropism) one or more external stimuli. ...

parapsychology

(Encyclopedia)parapsychology, study of mental phenomena not explainable by accepted principles of science. The organized, scientific investigation of paranormal phenomena began with the foundation (1882) of the Soc...

diode

(Encyclopedia)diode dīˈōd [key], two-terminal electronic device that permits current flow predominantly in only one direction. Most diodes are semiconductor devices; diode electron tubes are now used only for a ...

vision

(Encyclopedia)CE5 Optic nerve vision, physiological sense of sight by which the form, color, size, movements, and distance of objects are perceived. Defects of vision include astigmatism, color blindness, far...

Nicol prism

(Encyclopedia)Nicol prism nĭkˈəl [key], optical device invented (1828) by William Nicol of Edinburgh. It consists essentially of a crystal of calcite, or Iceland spar, that is cut at an angle into two equal piec...

Akasaki, Isamu

(Encyclopedia)Akasaki, Isamu, 1929–2021, Japanese physicist, b. Chiran, Japan, Kyoto Univ. (BA, 1942), Nagoya Univ. (Ph.D., 1964). Aftger graduating from college, Akasaki worked as an engineer before ...

reflection

(Encyclopedia)CE5 Image formation by curved mirrors and lenses reflection, return of a wave from a surface that it strikes into the medium through which it has traveled. The general principles governing the ref...

aureole, in physics

(Encyclopedia)aureole ôrˈēōlˌ [key], in physics, luminous circle seen when the sun or other bright light is observed through a diffuse medium, i.e., smoke, thin cloud, fog, haze, or mist. It sometimes occurs a...