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Choose an experiment:

Combustion
Titration
Exothermic
Rate of reaction 1
Rate of reaction 2
Rate of reaction 3
Rates - Colorimetry
Amylase
Aquarium
Breathing
Pulse
Fermentation
Lipase & fat
Food energy
Plant growth
Germination
Photosynthesis
Respiration
Insulation
Insulation - cups
Conducting
Conduction - window
Half-life
Pressure / temp
Pendulum
Battery types
Battery life
Capacitor
Current - Volt
Coil field
Thermistor

 
Half-life - How radioactive materials decay 
Radioactive materials decay, or lose their radioactivity, in a special and predictable way. If you have a fast decaying source, such as Protactinium with a half life of just 72 seconds, you can take a series of radioactivity readings and plot them on a graph. Or you can use a Geiger-Muller tube and radioactivity sensor connected to a computer. This can plot a radioactive decay curve and display it as it forms on the screen. Later you can analyse the results using your software. 
What you need

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Geiger-Muller tube / radioactivity sensor, clamp stand, radioactive source such as a Protactinium generator, data logging interface.

Setting up

Connect the Geiger-Muller tube to the sensor and the sensor to the interface. If the sensor is adjustable, set it to a suitable range.
Start your sensing software.
Set your sensing software to record for around 10 minutes. The exact time will depend the strength of the source. If you are using a Protactinium generator, give it a shake and then start recording.

Questions

How is decreasing radioactivity shown on your graph?
Does the radioactivity change in a steady 'straight-line' fashion?
Is the graph 'noisy'? Why might this be?
Use the software to calculate Ln (count rate) and plot this against time. How is this graph different? What does it tell us?
Use the software to perform a least squares fit on the decay curve.

Teacher question

You may have difficulty in obtaining replacement Protactinium generators as the suppliers have discontinued it because of leakage problems. What alternative could you suggest?

 

Activities in this section adapted from The IT in Science book of Data logging and Control. © IT in Science and may be reproduced as needed for use within your school.

 

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