Spark image

RADIOACTIVITY AND IONS

The early workers with radioactivity found that it could produce ions in a gas and this property has been used in all of the detectors of radiation. It is also the reason why radioactivity can be dangerous. You can show this ionising effect using the following simple experiment.

[TO BE DONE ONLY BY YOUR TEACHER]


Remove the glass side of a gold leaf electroscope and charge the electroscope with a polythene rod. Then hold a radium source near the leaf. The leaf will go down slowly showing that the charge has leaked away through the ions in the air. These ions have been made by the radioactivity passing through it.

(Using a match instead of the source will have the same effect and you should have seen that burning a match in air between two charged plates ionises the air between them and gives a current between the plates).


gold leaf electroscope animation

To see an animation of the gold leaf electroscope experiment click on the animation link.

The same effect can be shown by using a spark counter.

spark counter animation

To see an animation of the spark counter experiment click on the animation link.



 
A VERSION IN WORD IS AVAILABLE ON THE SCHOOLPHYSICS CD
 
 
 
© Keith Gibbs 2016