Question

The graph below shows the decay of a radioactive isotope. What is the half-life of the isotope?
A. 15 seconds
B. 25 seconds
C. 40 seconds
D. 200 seconds
The graph is in an attachment. :)

Answer 1

The half life is the time taken for the amount of a substance to become half of its original value. If we take the initial value to be 30 on the y-axis, the half of 30 is 15. We check the time at which the substance has reduced to 15 atoms and this is about 40 seconds. The answer is C.