Half-Life

Question 1

What type of process is radioactivity?

Answer 1

An entirely random process

Question 2

What is activity?

Answer 2

The rate at which a radioactive source decays

Question 3

What is activity measured in?

Answer 3

Activity is measured in becquerels, Bq

(1 Bq is 1 decay per second)

Question 4

Describe how a Geiger–Müller tube can be used to measure and detect radioactivity.

Answer 4

• A Geiger–Müller tube clicks each time it detects radiation
• The tube can be attached to a counter, which displays the count-rate (the number of clicks per second)

Question 5

Describe how photographic film can be used to detect radioactivity.

Answer 5

The more radiation the film is exposed to, the darker it becomes

Question 6

It cannot be predicted when a particular nucleus will decay.

If there are lots of nuclei though, how can you predict how many will have decayed in a given time?

Answer 6

This can be predicted based on the half-life of the source

Question 7

State what is meant by half-life.

Answer 7

The average time taken for the number of radioactive nuclei in an isotope to halve

(average time taken for the activity of a source to decay by half)

Question 8

What does a short half-life indicate?

Answer 8

• This means the activity of a source falls quickly
• This is because the nuclei are very unstable and rapidly decay

Question 9

What does a long half-life indicate?

Answer 9

• This means the activity of a source falls slowly
• This is because most of the nuclei don’t decay for a long time
• (The source sits there, releasing small amounts of radiation for a long time)

Question 10

(Exam-style question)

Answer 10