ray (ra)
grenz rays
1. a line emanating from a center.
2. a more or less distinct portion of radiant energy (light or heat), proceeding in a specific direction.
α-rays , alpha rays high-speed helium nuclei ejected from radioactive substances; they have less penetrating power than beta rays.
β-rays , beta rays electrons ejected from radioactive substances with velocities as high as 0.98 of the velocity of light; they have more penetrating power than alpha rays, but less than gamma rays.
digital ray
1. a digit of the hand or foot and the corresponding portion of the metacarpus or metatarsus, considered as a continuous structural unit.
2. in the embryo, a mesenchymal condensation of the hand or foot plate that outlines the pattern of a future digit.
γ-rays , gamma rays electromagnetic radiation of short wavelengths emitted by an atomic nucleus during a nuclear reaction, consisting of high-energy photons, having no mass and no electric charge, and traveling with the speed of light and with great penetrating power.
grenz rays very soft x-rays having wavelengths about 20 nm, lying between x-rays and ultraviolet rays.
medullary rays the intracortical prolongations of the renal pyramids.
roentgen rays x-r's.
x-rays electromagnetic vibrations of short wavelengths (approximately 0.01 to 10 nm) or corresponding quanta that are produced when electrons moving at high velocity impinge on various substances; they are commonly generated by passing high-voltage current (approximately 10,000 volts) through a Coolidge tube. They are able to penetrate most substances to some extent, to affect a photographic plate, to cause certain substances to fluoresce, and to strongly ionize tissue.
grenz rays (gr nts)pl.n. Very soft x-rays, closely allied to ultraviolet rays in their wavelength and in their biological action upon tissues. |
grenz rays
Etymology: Ger, Grenze, boundary; L, radius, ray
low-energy x-rays, used for treatment of skin conditions, that have very little penetrating ability and are frequently applied by dermatologists rather than by radiotherapists.
grenz rays
very soft electromagnetic radiation of wavelengths about 2 Å.
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