Modelling Decay

Question 1

Define the activity of an unstable nucleus.

Answer 1

Activity is the rate at which a source of

unstable nuclei decays.

Question 2

What is the unit of radioactive activity?

Answer 2

Becquerel (Bq)

Question 3

What is count-rate?

Answer 3

The number of radioactive decays per

second for a radioactive source.

Question 4

Give an example of a detector that may be used to

measure count-rate.

Answer 4

Geiger-Muller tube

Question 5

Describe the nature of radioactive decay

Answer 5

● Random
● Which nuclei decays and when is
determined only by chance
● It is impossible to predict which nuclei
will decay and when

Question 6

Define the half-life of a radioactive isotope

Answer 6

● The time it takes for the number of
unstable nuclei in a substance to halve
● The time it takes for the count rate
from a sample to fall to half its initial
level