1.) If two different radioisotopes A and B have the same activity but the half-l

ID: 2103014 • Letter: 1

Question

1.) If two different radioisotopes A and B have the same activity but the half-life of

isotope A is larger than the half-life of isotope B, what is the relative magnitude of

the numbers of radioactive nuclei of isotope, A to isotope B?

2. )A unit of activity called the curie is defined as 3.7 x 1010 disintegrations/second.

What is the activity in microcuries of an strontium source that emits 2250 beta

particles per minute? (1 microcurie = 10-6 curies).

3.) The half-life of radioactive phosphorus (P-32) is 14.3 days. If a solution containing

10 microcuries is purchased for an experiment on the absorption of phosphates by

plants, what would the activity be after 21 days?

1)as B disintegrates faster ,A has more nuclei than B at a given time t

2)3.7*10^10=1curie

2250/60 =x curie

x=2250/(60*3.7*10^10)=10.135135*10^-10curie

=10.1*10^-4 microcurie

3)A=A0e^(-0.693t/thalf)

=10*10^-6 *e^(-0.693*21/14.3)

=3.61microcurie

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