Geometric unsharpness in radiographic imaging is directly proportional to which of the following?

Geometric unsharpness in radiographic imaging refers to the blurring or loss of detail in an image that can occur due to variations in the geometry of the imaging setup. It is primarily influenced by the distance between the focal spot of the x-ray tube and the imaging receptor, as well as the distance from the object to the receptor.

In this context, the correct option relates to the notion that geometric unsharpness increases with greater distances because the rays diverge more as they travel. Specifically, if the distance from the target (focal spot of the x-ray tube) to the imaging receptor is increased, the penumbra (the area of partial shadow) becomes larger, which in turn increases the unsharpness of the image.

Therefore, the correct choice highlights a key aspect of how unsharpness varies with distance in a radiographic setup, indicating that as this distance increases, the geometric unsharpness also increases proportionally. The other options do not directly correlate with the principle of geometric unsharpness in the same manner. For example, while exposure time and x-ray tube voltage affect image density and contrast, they do not specifically address the geometric factors contributing to unsharpness.