Film badge
Definition and meaning of Film badge in chemistry.
Film badge is a personal radiation dosimeter that uses a small piece of photographic film, sealed behind filters of varying thickness and material, to measure a wearer's cumulative exposure to ionizing radiation. Ionizing radiation striking the film produces silver grains upon development, and the degree of darkening indicates the absorbed dose.
In more detail
The badge's film is packaged with several small metal filters (typically aluminum, copper, and lead) positioned over different regions of the film. Because different filters attenuate beta, gamma, and X-radiation to different extents, comparing the darkening pattern beneath each filter lets a technician estimate both the dose received and, roughly, the type and energy of radiation involved. Film badges are not effective at detecting alpha particles, since alpha particles have such a short range that they cannot penetrate the light-tight wrapping that shields the film from ambient light. Badges are worn by workers in nuclear, medical, and industrial settings and are periodically collected and developed to track long-term occupational exposure, serving as a legal and safety record.
Key facts
| Field | Physical Chemistry |
|---|---|
| Detects | Beta, gamma, and X-radiation (not alpha, which cannot penetrate the film's protective wrapping) |
| Active component | Silver halide photographic emulsion |
| Typical wear period | 1 month before processing |
A hospital radiology technician wears a film badge clipped to their lab coat; after one month it is sent to a processing lab, where the developed film's optical density beneath each filter is compared to a calibration standard to calculate the technician's monthly radiation dose in millisieverts.
Frequently asked questions
How is the radiation dose read from a film badge?
After development, the film's optical density (darkening) beneath each filter is measured with a densitometer and compared to film exposed to known reference doses, converting darkening into an estimated absorbed dose.
Have film badges been replaced by newer technology?
In many facilities, yes, thermoluminescent dosimeters (TLDs) and optically stimulated luminescence (OSL) badges have largely replaced film badges because they offer better sensitivity and are easier to process, though film badges are still used in some settings.