urgent questions

2010-12-22 11:27 pm

1. An alpha-emitting radioactive soe rodes anzat cuen 3.2 x 10^-6 A when it is placed inside an ionization chamber. If each alpha particle produces 2x 10^5 ion pairs, find the activity of the source. (Take e= -1.6x 10^-19C and assume that the ions are singly charged and that all are collected.)

2. Why is it necessary to calculate the mean value of several count rates foreach thickness?

更新1:

An alpha-emitting radioactive source produces an ionization current3.2 x 10^-6

回答 (1)

天同

2010-12-23 12:34 am

✔ 最佳答案

1. No. of ions produced in one second = 3.2x10^-6/1.6x10^-19 = 2 x 10^13
Since each alpha particle produces 2 x 10^5 ion pairs,
hence, no. alpha particles = 2 x10^13/2x10^5 = 10^8

Assume there is no self absorption of alpha particles within the radioactive source,
activity of the apha source = 10^8 Bq = 100 MBq

2. I suppose you refer to an experiment on penetration or absorption of radiation by materials of different thicknesses.

Radioactive counting is a random process. A single reading is subject to large statistical uncertainty. Hence, it is always advisable to take several readings in order to minimize the statistical uncertainty.

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