Final answer:
The PA projection is a technique used in medical imaging where the x-ray beam passes through the patient's body from the back to the front. This allows for obtaining a posterior-anterior view and capturing images of internal structures.
Step-by-step explanation:
When taking a film in the PA projection, the x-ray beam passes through the patient. This projection is commonly used in medical imaging to obtain a posterior-anterior view of the body. In this position, the x-ray machine is positioned behind the patient, and the x-ray beam enters the body from the back (posterior) and exits at the front (anterior). This allows the x-ray to pass through the patient's body, capturing an image of the internal structures.