A hospital physicist measure the strength of a cobalt - 60 X-Ray machine every year. His result over a six year period are shown in the table. Strength is measured in MBq (megabecquerels) or millions of counts per second.
Strength (MBq) C 10.0 8.8 7.8 6.9 6.1 5.4 4.8
Time t (years) 0.0 1.0 2.0 3.0 4.0 5.0 6.0
a) Plot a graph of strength in MBq (vertical axis) against time in years (horizontal axis).
b) Describe the relationship between strength and time in words.
c) What is the value of the half life of 60 Co?
A completed graph and answer to the problem!