Physics – 5.2.1 Detection of radioactivity | e-Consult

Three factors that could affect the reading on the counter are:

• Distance from the source: The intensity of radiation decreases with the square of the distance from the source (inverse square law). As the distance increases, the radiation reaching the Geiger-Müller tube decreases, resulting in a lower count rate on the counter.
• Shielding: Placing a shield (e.g., lead) between the source and the Geiger-Müller tube will absorb some of the radiation. The amount of radiation reaching the tube will be reduced, leading to a lower count rate on the counter. The effectiveness of the shielding depends on the type of radiation and the thickness of the material.
• Type of radioactive decay: Different types of radioactive decay (alpha, beta, gamma) have different penetrating powers. A source emitting gamma radiation will generally produce a higher count rate than a source emitting alpha radiation at the same activity, as gamma radiation is less easily absorbed by matter.