Radioactive Decay & Half Life
This lesson covers:
- What the terms 'activity' and 'half-life' mean
- How to interpret a graph of radioactive decay
- How to calculate the activity and half-life of a radioactive material
Which of the following describes the decay process for a single atom?
The decay occurs at regular intervals
The decay is random
|
magnitude / rate / isotopes
'Activity' is the overall of decay of all of the radioactive in our sample.
|
We measure radioactive activity as the average number of decays per second.
What are the units of activity?
Volts (V)
Teslas (T)
Becquerels (Bq)
Webers (Wb)
|
Which of the following are definitions for the 'half-life' of a radioactive sample?
(Select all that apply)
The time taken for the nuclei to lose half their electrons
The time taken for the activity to half
The time taken for the number of radioactive nuclei in a sample to halve
|
True or false? As a radioactive sample decays over time, its half life decreases.
True
False
|
The above graph shows a radioactive decay curve.
What is the half-life of the material?
s
|
The above graph shows three different radioactive materials.
Which graph shows the radioactive material with the shortest half-life?
A
B
C
|
What device is used to record radioactive decays?
Voltmeter
Oscilloscope
Galvanometer
Geiger-Muller tube and counter
|
The activity of a radioactive material started at 240 Bq and is now 30 Bq.
How many half-lives have elapsed?
half-lives
|
The activity of a radioactive material is 800 Bq and its half-life is 5 hours.
What is the activity of the radioactive material after 15 hours?
Bq
|
A radioactive isotope has a half-life of 10 minutes.
If the activity was initially 800 Bq, calculate how long it would take for the activity to fall to 50 Bq.
min
|