When a x-ray photograph is taken why is it necessary to have the film in a light proof cassette?

Answer 1

Film is light sensitive so any exposure to the film will fog it. Most film comes either in a cassette, as in 35mm or roll-film which is protected by a paper leader and trailer. Professionals also use cut film which is hand loaded in the dark into film holders. Once a film is exposed in the camera it has what is called a latent image. It stays latent until processed. Once all the film is exposed it needs to be processed as soon as possible. Once the film is exposed its sensitivity makes it more susceptible to fogging and therefor must be protected from light. In the case of 35 mm and 120 roll film it shouldn't be much of a problem as the film is protected by the cassette or the backing paper. Once the film is taken out of its protection it has to be in total darkness. Colour film is sensitive to all colours and light. Monochrome film is what is called panchromatic. This means that although the film is mono it still records colours as grey tones so it must be handled in complete darkness. Black and white papers as used for monochrome prints are sensitive to only certain colours of the visible spectrum so can be viewed under dim yellow light. Blue light would fog the paper which is why in a black and white darkroom yellow filters are used for processing paper prints.

Answer 2

The film is light sensitive and if it wasn't in a light proof cassette then the film would be surrounded by light so the picture that it takes would be ruined.