positive rays
121microscope — /muy kreuh skohp /, n. 1. an optical instrument having a magnifying lens or a combination of lenses for inspecting objects too small to be seen or too small to be seen distinctly and in detail by the unaided eye. 2. (cap.) Astron. the… …
122Solar variation — Solar variations are changes in the amount of solar radiation emitted by the Sun. There are periodic components to these variations, the principal one being the 11 year solar cycle (or sunspot cycle), as well as aperiodic fluctuations. Solar… …
123Cardinal point (optics) — For other uses, see Cardinal point (disambiguation). In Gaussian optics, the cardinal points consist of three pairs of points located on the optical axis of an ideal, rotationally symmetric, focal, optical system. For ideal systems, the basic… …
124nebula — 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 …
125Computed tomography — tomos (slice) and graphein (to write).Computed tomography was originally known as the EMI scan as it was developed at a research branch of EMI, a company best known today for its music and recording business. It was later known as computed axial… …
126Lichtenberg figure — Lichtenberg figures (Lichtenberg Figuren, or Lichtenberg Dust Figures ) are branching electric discharges that sometimes appear on the surface or the interior of insulating materials. They are named after the German physicist Georg Christoph… …
127therapeutics — /ther euh pyooh tiks/, n. (used with a sing. v.) the branch of medicine concerned with the remedial treatment of disease. [1665 75; see THERAPEUTIC, ICS] * * * Treatment and care to combat disease or alleviate pain or injury. Its tools include… …
128actinide element — ▪ chemical element group Introduction any of a series of 15 consecutive chemical elements in the periodic table from actinium to lawrencium (atomic numbers 89–103). As a group they are significant largely because of their radioactivity.… …
