A question related to radioactivity.

by DarkStalker
Tags: decay, decay constant, radioactivity, uncertainty
DarkStalker is offline
May4-11, 10:59 AM
P: 26
1. A cobalt-60 source having a half-life of 5.27 years is calibrated and found to have an
activity of 3.50 105 Bq. The uncertainty in the calibration is 2%.
Calculate the length of time, in days, after the calibration has been made, for the stated
activity of 3.50 105 Bq to have a maximum possible error of 10%.

A= -лN, where A= Activity, л=Decay Constant and N=Original number of nuclides.

n=Ne^(-лt), where n=number of undecayed nuclides, N= original number of nuclides, л=decay constant and t=time.

3. The attempt at a solution: None

I am utterly stumped at this one. Truthfully I didn't even understand the question properly. I can't make a connection between this uncertainty and decay. I have the solution but that didn't help me much. Here it is:

source must decay by 8%
A = A0 exp(–ln2 t / T) or A/ A0 = 1 / (2t/T)
0.92 = exp(–ln2 t / 5.27) or 0.92 = 1 / (2t/5.27)
t = 0.634 years
= 230 days
(allow 2 marks for A/ A0 = 0.08, answer 7010 days
allow 1 mark for A/ A0 = 0.12, answer 5880 days)

Could someone please explain to me what exactly the question asks for, and how the quantities are related? Thanks in advance.
Phys.Org News Partner Science news on Phys.org
Simplicity is key to co-operative robots
Chemical vapor deposition used to grow atomic layer materials on top of each other
Earliest ancestor of land herbivores discovered
factfinder is offline
Apr26-12, 08:38 PM
P: 8
CIE a level physics paper 4. the question was made to be unanswered i guess.

Register to reply

Related Discussions
One last Radioactivity Question!! Advanced Physics Homework 0
Radioactivity Question General Physics 4
URGENT HELP Question About Radioactivity Advanced Physics Homework 2
Physics: radioactivity question? Introductory Physics Homework 1
Strange radioactivity question. Atomic, Solid State, Comp. Physics 5