What is the primary function of a grid on an x-ray table?

The primary function of a grid on an x-ray table is to prevent scatter radiation from reaching the film. Scatter radiation occurs when the x-ray beams interact with matter and change direction, which can degrade the quality of the image produced. By utilizing a grid, which typically consists of alternating strips of lead and plastic, the grid effectively absorbs or deflects this scatter radiation while allowing the primary x-ray beams to pass through. This results in a clearer and more contrasted image, making it easier to visualize the structures being imaged.

The other options do not accurately describe the primary purpose of the grid. While decreasing exposure is a benefit that can arise from improved image quality when using a grid, it is not the main function of the grid itself. Grids do not provide a reliable scale for measuring structures, nor are they used to prevent light exposure on the film, as this task is handled by other means within the imaging process.