ˌradioacˈtivity
Also with hyphen.
[f. radio- 2 + activity.]
1. a. The property or condition of being radioactive; (the field of study concerned with) the phenomena displayed by radioactive materials. Hence, the radiation emitted by a radioactive material, or such material itself in a dispersed form.
| 1899 Nature Nov. 71/1 On the radio-activity induced by the Becquerel rays. 1900 P. Kropotkin in 19th Cent. Dec. 932 They communicate radio-activity..to the surface of the bodies. 1902 Harper's Mag. Aug. 364/1 For days Professor Curie was unable to approach his electrometers..owing to his acquired radio⁓activity. 1920 Discovery Apr. 122/1 This was the first discovery in the science which later became known as radio⁓activity. 1947 Sci. News V. 55 Between them, these three series of radioactive elements include the whole of the known natural sources of radioactivity. 1955 Sci. Amer. Aug. 35/1 Radioactivity is measured in curies: one curie is equal to the radioactivity from one gram of radium (37 billion atoms disintegrating per second). 1955 Bull. Atomic Scientists Sept. 253/1 Radioactivity can travel in the air over large distances, and its very nature and action are unknown and unfamiliar to most people. 1962 S. G. Waley in A. Pirie Lens Metabolism Rel. Cataract 359 When the enzyme is treated with isotopically labelled iodoacetate..and the enzyme is boiled, no radio-activity is released. 1969 Daily Tel. 23 Jan. 1/4 A small Swiss nuclear research and training reactor at Lucens was closed yesterday after developing a leak of radio-activity. 1978 L. Deighton SS-GB xvi. 135 Do you know what radio-activity is?.. It's the emission of radiation from unstable atomic nuclei—alpha particles, nucleons, gamma rays, electrons and so on. |
b. fig.
| 1922 C. E. Montague Disenchantment (1924) xv. 210 In men and women of high mental vitality, in places where any of the radio-activity of gifted teaching breaks out for a while..the mind is easily delighted. 1928 Manch. Guardian Weekly 27 July 74/1 That radio-activity and that consummate technique shine out from poem after poem. |
2. The property of emitting radio waves.
| 1959 Sci. Amer. Feb. 66/1 (Advt.), This is Messier 87—one of many galaxies and nebulae radiating radio energy throughout time and space. What primeval force motivates this celestial radioactivity? 1972 Nature 20 Oct. 440/2 It seems unlikely that Cygnus X-3 is unique with respect to its radioactivity and it may therefore represent only one member of a large number of objects that exhibit highly variable radio emission, and which may have been overlooked in classical radio surveys. 1978 Ibid. 11 May 131/1 We show here that these non-Io-related..decametric radio activities are affected by solar wind conditions around Jupiter. |