Edexcel iGCSE Physics -7.9 Detection of Ionising Radiation- Study Notes- New Syllabus

Detecting Ionising Radiation

Ionising radiation cannot be seen directly, but it can be detected using suitable devices. Two commonly used detectors are photographic film and the Geiger–Müller detector.

Key Statement

Statement: Photographic film and a Geiger–Müller detector can be used to detect ionising radiations.

Key idea: These detectors work because ionising radiation affects matter.

Photographic Film 

How it works:

• Photographic film is sensitive to ionising radiation.
• Radiation darkens the film by ionising atoms in the emulsion.
• Greater exposure produces darker film.

Uses:

• Monitoring radiation exposure of workers.
• Personal dosimeters worn over long periods.

Limitation:

• Does not give immediate readings.
• Must be developed to see results.

Geiger–Müller Detector

How it works:

• Contains gas at low pressure inside a tube.
• Ionising radiation enters the tube.
• The gas becomes ionised.
• This produces an electrical pulse.

Output:

• Each pulse represents a detection event.
• Pulses can be counted electronically.
• Results are obtained immediately.

Key idea: Higher count rate → higher radiation intensity.

Comparing the Two Detectors

• Photographic film gives cumulative exposure.
• Geiger–Müller detector gives instant readings.
• Both rely on ionisation.