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