Final answer:
Radiographs with high-frequency grids show less distinct grid lines because the dense packing of the grid lines makes them less visible, resulting in a more even image. This contrasts with low-frequency grids, where the individual lines are more discernible.
Step-by-step explanation:
The fewer distinct grid lines on a radiograph compared to those with low frequency are due to the differences in the frequency of the grids themselves. Grids used in radiology are designed to absorb scattered radiation, thereby improving image quality. A high-frequency grid has more grid lines per inch than a low-frequency grid.
The high density of the grid lines in a high-frequency grid makes the individual lines less discernible to the eye or the imaging system, resulting in a more uniform appearance without prominent grid lines impacting the image. In contrast, a low-frequency grid has fewer lines per inch, which makes the grid lines more visible on the radiograph.
In relation to electromagnetic radiation, it is important to note that high-frequency radiation (e.g., X-rays) carries more energy than low-frequency radiation (e.g., radio waves). However, since the original question deals with grid frequencies in radiographs, the energy of the electromagnetic radiation is not the primary concern but rather the frequency of the grid lines.