Common Misconceptions

⚠️ Common Misconceptions

Misconception 1: "A GM tube measures the activity of a source directly"

A GM tube measures count rate — the number of events it detects per unit time. This is related to but not equal to the true activity of the source (decays per second). Not every decay produces a detectable particle, not every particle enters the tube, and the tube does not detect every particle that enters it. Count rate is an indirect measure of activity.

Misconception 2: "A cloud chamber can detect gamma radiation as tracks"

Gamma radiation is electromagnetic — it carries no charge and does not directly ionise along a straight path. Therefore, gamma does not leave visible tracks in a cloud chamber. Only charged particles (alpha and beta) produce visible tracks. Gamma can only be indirectly detected in a cloud chamber through occasional secondary ionisation events.

Misconception 3: "Film badges protect workers from radiation"

Film badges are dosimeters — they monitor how much radiation a person has received, but they provide no shielding or protection. They simply keep a record of exposure. Actual protection comes from shielding (lead, concrete), distance from sources, and minimising exposure time.

Misconception 4: "Count rate and activity are the same thing"

Activity is measured in becquerels (Bq) and refers to the number of actual decays per second in the source. Count rate is the number of events detected by the detector per second or minute. These are different: a source might have a high activity but give a low count rate if the detector is far away or if the radiation type has low penetrating power.