Using Photographic Film:
When exposed to ionising radioation, photographic film becomes fogged. This method was first used by Henri Becquerel in 1896 but it is still used today to show when scientists dealing with radioactive materials become exposed to a certain anount of radiation.
The Geiger-Müller Tube:
It is a glass tube containing a special mixture of gases at very low pressure. The inside is lined with an electrically conducting coating. In the centre of the tube, there is an electrode connected to a high voltage supply.
When ionising radiation enters the tube, it causes the gas inside to form ions, allowing a pulse of current to flow from the electrode to the conducting layer. This is detected by an electronic circuit.
The GM tube is linked to a counting circuit or a rate meter which keeps a count of how much ionising radiation has entered the tube or measures the number of ionising events per second.
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