Final answer:
Underexposure of an image in a film-screen system can result from insufficient mAs, insufficient kV, or insufficient development. These factors contribute to a darker image due to inadequate exposure to radiation or incomplete chemical processing of the film.
Step-by-step explanation:
​When we discuss underexposure in the context of film-screen systems in radiography, it refers to a condition where the image appears too dark due to insufficient exposure to the radiographic film. Insufficient exposure can occur because of various reasons, one being insufficient mAs (milliampere-seconds), which is the product of the electric current and the time that the film is exposed to radiation. Previous knowledge indicates that the more radiation the film is subjected to, the more exposed it becomes, linking directly to the mAs value.
Another potential cause for underexposure is insufficient kV (kilovolt). The kV refers to the peak voltage applied to the x-ray tube and affects the energy of the x-rays produced. Low kV results in lower energy x-rays that might not sufficiently penetrate the subject to create an adequate exposure on the film.
The last cause the student's question refers to is insufficient development, referring to the chemical process that transforms the latent image on a film into a visible image. If the development time in the chemical solution is too short, or if the solution is too cold or depleted of chemical activity, it may lead to underdeveloped images which also appear underexposed.