Half Life

Question 1

what can radiation be measured by

Answer 1

Geiger-Muller tube / counter: records the count rate

Question 2

Activity =

Answer 2

overall rate of decay of all the isotope in a sample

Question 3

what is activity measured in

Answer 3

Becquerels (Bq) - 1Bq = 1 decay per second

Question 4

Half life =

Answer 4

the time taken for the no. of radioactive nuclei of the isotope in a sample to halve
OR
time taken for the count rate (or activity) from a sample containing the isotope to fall to half

Question 5

Radioactive decay is ………….

Answer 5

random

Question 6

what does a short half-life mean and why could it be dangerous

Answer 6

• activity falls quickly –> nuclei is very unstable + decays rapidly
• dangerous because of high amount of radiation emitted at the start - quickly become safe

Question 7

what does a long half-life mean and why could it be dangerous

Answer 7

• activity falls slower - most of the nuclei don’t decay for a long time –> just releases small amounts
• Dangerous = nearby areas are exposed to radiation for years

Question 8

The half-life of cobalt-60 is 5 years. If there are 100 g of cobalt-60 in a sample, how much will be left after 15 years?

Answer 8

100 / 2 = 50
50/2 = 25
25/2 = 12.5g