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翻訳と辞書　辞書検索 [ 開発暫定版 ] スポンサード リンク Specific activity ： ウィキペディア英語版 Specific activity Specific activity is the activity per quantity of a radionuclide and is a physical property of that radionuclide. Activity is a quantity related to radioactivity. The SI unit of activity is the becquerel (Bq), equal to one reciprocal second. Since the probability of radioactive decay for a given radionuclide is a fixed physical quantity (with some slight exceptions, see Changing decay rates), the number of decays that occur in a given time of a specific number of atoms of that radionuclide is also a fixed physical quantity (if there are large enough numbers of atoms to ignore statistical fluctuations). Thus, specific activity is defined as the activity per quantity of atoms of a particular radionuclide. It is usually given in units of Bq/g, but another commonly used unit of activity is the curie (Ci) allowing the definition of specific activity in Ci/g. == Half-life == Experimentally-measured specific activity can be used to calculate the half-life of a radionuclide. Half-life (T1/2) is defined as the length of time for half of a given quantity of radioactive atoms to undergo radioactive decay: Or more generally: Starting with ''N0'', atoms of an element, the number of atoms, ''N'', remaining after time, ''t'', is given by: : $N=N\_0\backslash left(\backslash frac\backslash right)^$ The natural log of both sides : $\backslash ln(N)=\backslash ln(N\_0)+\backslash left(\backslash frac\backslash right)\backslash ln\backslash left(\backslash frac\backslash right)$ The derivative with respect to time, ''t'' : $\backslash frac\backslash frac=\backslash frac\backslash right)\}$ Multiplying both sides by ''N'' : $\backslash frac=\backslash frac\backslash right)\}$ Yields : $\backslash frac=\backslash frac$ ''dN''/''dt'' represents the decay rate of atoms. The negative sign shows that the rate is negative, so the number of atoms is decreasing with time. Rearranging terms: : $T\_=\backslash frac\; \}$ 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Specific activity」の詳細全文を読む スポンサード リンク 翻訳と辞書 : 翻訳のためのインターネットリソース Copyright(C) kotoba.ne.jp 1997-2016. All Rights Reserved.