Direct visual examination is possible when the eye can be placed within what distance of the inspection surface?

The option indicating a distance of 610 mm (24 in.) is accurate as it aligns with the standard practice for direct visual examination. This distance allows for sufficient clarity and resolution when an inspector is assessing surfaces for defects, irregularities, or other visual characteristics. At this range, the inspector can effectively use their eyesight to capture fine details while minimizing distortion and potential obstructions.

Being too close or too far from the inspection surface may hinder the quality of the visual inspection. Distances shorter than 610 mm could result in perspective distortion and may lead to missing finer points of observation, whereas distances greater than this can reduce the ability to discern small details that could be critical in a visual inspection process. By adhering to the 610 mm distance, inspectors can maintain a balance that facilitates thorough observation and effective evaluation of the surface conditions.