Film Badges and Photographic Detection

⚛️ Film Badges and Photographic Detection

Figure 3: A film badge dosimeter — different windows allow different radiation types to reach specific film areas, enabling identification and dose measurement

Workers in environments with potential radiation exposure (hospitals, nuclear industry, research laboratories) wear film badges to monitor their personal radiation dose.

How Film Badges Work

Film badges contain a small piece of photographic film — similar to old camera film — that is darkened by exposure to ionising radiation. The more radiation absorbed, the darker the film becomes.

The badge has several compartments with different materials in front of the film:

• Open window — no material, so all radiation (alpha, beta, gamma) can reach the film. Comparing this area with others tells you the total dose.
• Plastic filter — blocks alpha but lets beta and gamma through. Comparison with the open window reveals alpha contribution.
• Aluminium filter — blocks both alpha and low-energy beta. Only gamma (and high-energy beta) penetrate.
• Lead/tin filter — blocks all but the most energetic gamma radiation.

By developing the film and comparing the darkening in each section, a radiation safety physicist can determine not only the total dose but also what types of radiation the worker was exposed to.

Advantages and Disadvantages of Film Badges

Advantages: Cheap, passive (no power needed), permanent record of exposure, can distinguish between radiation types, accumulate dose over time (so a monthly total is recorded).

Disadvantages: Cannot give a real-time reading (must be developed), film degrades over time, cannot be used again once developed.