Calcium-45 decays by beta emission. How many (3 particles are emitted over a 9.0
ID: 971159 • Letter: C
Question
Calcium-45 decays by beta emission. How many (3 particles are emitted over a 9.00 minute time period by a sample of ^45 Ca that has an activity of 45.0 millicuries? A 90.0 kg worker is exposed to the radiation source above for a period of 9.00 minutes. The kinetic energy of each emitted beta particle is 4.13 Times 10^-14 J. If the worker's body absorbs 19.0 percent of the beta particles emitted over that time period, what is the worker's exposure in millirems? The Relative Biological Effectiveness (RBE) factor for beta particles is 1.Explanation / Answer
A curie is a unit of radioactivity which is corresponding to 3.7 × 1010 disintegrations per second.
Here 45.0 millicuries means 0.045 curies
Measn 0.045 x 3.7 x 10^10 disintegrations per second
1.665 x 10^9 disintegrations per second
Now calculate the total disintegrations after 9.0 min as follows:
9.0 min * (60sec/1min) x (1.665 x 10^9 disintegrations/1sec)
8.99 x 10^11 disintgrations.