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e of luminescence under the action of cathode rays, X rays, or any of the allied forms of radiation. -- Ra`di*o- ac*tiv"i*ty, n.

The use of the radiometer, or the measurement of radiation. -- Ra`di*o*met"ric (#), a.

for maintaining themselves at a higher temperature than their surroundings, and for their radiations, which are of three kinds: alpha rays, beta rays, and gamma rays (see these terms). By reason of these rays they ionize gases, affect photographic plates, cause sores on the skin, and produce many other striking effects…

One of the component elements of the total radiation from a body; any definite or limited portion of the spectrum; as, the red ray; the violet ray. See Illust. under Light.

Radiation of light. [Obs.]

all I have wherewith to answer him. Ps. cxix. 42. The wherewith to meet excessive loss by radiation. H. Spencer.

The widening and duplication, triplication, etc., of spectral lines when the radiations emanate in a strong magnetic field, first observed in 1896 by P. Zeeman, a Dutch physicist, and regarded as an important confirmation of the electromagnetic theory of light.