How can radiation be detected using film badges?

When exposed to ionising radiation, photographic film will turn from being transparent to dark and non transparent on each side of the film badge are various 'windows' the open window allows all types of radiation through, therefore showing exposure to beta and gamma radiation one set of windows are plastic of different thicknesses allowing the person examining the film to tell what kinds of beta radiation they have been exposed to another set of windows are different types of metals (including lead and tin) allowing the detection of gamma rays and other ionising radiation the final exposure of the film will show how much and what kind of radiation someone has been exposed to