最近做past paper 有1題5係太明點做
條題目係咁:
Rn-222的半衰期為3.8日,若Rn-222的初質量為1+10^-5,估算15.2日後未衰變的Rn-222的質量
我睇完答案刀5係好明,因為佢只有1條式咁計落去
想請問計呢種數係米有公式既呢?
如果無既請問又要點計呢?
thx
關於會考物理核衰變問題
2010-04-03 10:54 pm
回答 (2)
2010-04-05 1:57 am
✔ 最佳答案
這些題目其實頗為容易次次都係禁計嫁la!
首先找出15.2日內Rn-222做左幾多次半衰期先
所以就將15.2/3.8 .計到係做左4 次半衰期.
而每一次半衰期,Rn-222的質量就會減半.
所以就將初質量1+10^-5除(2^4)
就會得出衰變後的質量為6.25x10^-4
由此就得出公式
衰變後的質量=初質量/[2^(元素未衰變的日子/元素的半衰期)]
2010-04-03 11:55 pm
The formula is: m = M/2^n
where m is the mass (or the number of nuclidei) left
M is the original mass (or the original number of nuclei) present
n = no. of half-lives, i.e. n = t/T, where t is the decay time, and T is the half-life.
In your example, n = 15.2/3.8 = 4
hence, m = 1 x 10^-5/2^4 kg = 6.25 x 10^-7 kg
where m is the mass (or the number of nuclidei) left
M is the original mass (or the original number of nuclei) present
n = no. of half-lives, i.e. n = t/T, where t is the decay time, and T is the half-life.
In your example, n = 15.2/3.8 = 4
hence, m = 1 x 10^-5/2^4 kg = 6.25 x 10^-7 kg
收錄日期: 2021-04-29 17:35:15
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