In an x-ray examination, changing the source-to-image distance from 72 inches to 40 inches will result in which effect?

Changing the source-to-image distance (SID) has a significant impact on the intensity of the x-ray beam that reaches the image receptor. When the SID is decreased from 72 inches to 40 inches, the x-ray beam intensity increases.

This effect can be understood through the inverse square law, which states that the intensity of radiation is inversely proportional to the square of the distance from the source. In simpler terms, as the distance from the x-ray source decreases, the intensity of the x-ray beam increases because the x-rays are more concentrated over a smaller area.

Since the distance is reduced, the same amount of radiation is being delivered to a smaller target area, resulting in a higher intensity of the x-ray beam. This is a crucial factor in x-ray imaging as greater intensity can lead to better exposure and potentially improved image quality, provided that other exposure factors are managed properly to avoid overexposure.

This direct relationship between SID and beam intensity underlines the importance of understanding exposure parameters in radiographic practice.