What effect does decreasing object-screen distance have?

Decreasing the object-screen distance directly impacts the magnification of the radiographic image. When the distance between the object being imaged (such as a body part) and the image receptor (screen or film) is reduced, the radiographic result will show less magnification. This happens because the x-rays have a more direct path to the receptor, leading to a more accurate representation of the object’s size and shape.

In radiography, magnification occurs when the x-ray source is significantly farther from the object than the image receptor, causing the image to appear larger than the actual object. Therefore, bringing the object closer to the image receptor decreases the likelihood of this enlargement effect, resulting in a more precise depiction of the original dimensions of the object.

In addition, the other options relate to various factors that could affect imaging but are not relevant in this scenario. For example, magnification is specifically tied to the distances involved in radiography rather than exposure time or being unaffected. Hence, it's clear why reducing the distance between the object and the screen effectively decreases magnification.