When radiation is measured by an ionization chamber, the measurement occurs because the radiation what?

• A. passes through the chamber without interacting
• B. interacts with the metal housing of the chamber
• C. ionizes the air in the chamber
• D. discharges electrical components in the chamber

Answer: (C)

The measurement comes from ionization of the air inside the chamber. When radiation enters, it interacts with air molecules and creates ion pairs (positive ions and free electrons). The chamber applies an electric field, pulling the charges to the electrodes and generating a current. The size of that current is proportional to the radiation intensity, allowing the instrument to read the dose rate. If the radiation passed through without interacting, or interacted mainly with the housing, there would be no ionization current produced in the gas. Discharging electrical components isn’t how the signal is generated.