Which characteristic distinguishes a Class 3R laser?

A Class 3R laser is defined by its ability to potentially cause eye damage when viewed directly. This means that while it is not as hazardous as higher class lasers, there is still a risk if one looks directly into the beam. It is important to adhere to safety precautions when handling or being in proximity to Class 3R lasers, especially in environments where accidental direct viewing may occur.

In contrast, the other characteristics do not accurately represent Class 3R lasers. For instance, while they are indeed lower in risk compared to higher classes, they are not considered completely safe for all viewing conditions, which underscores the importance of proper safety measures. Likewise, Class 3R lasers generally have a power output limit of 5 mW, not 500 mW. Finally, they can operate within the visible light spectrum, as a defining feature is that many Class 3R lasers emit visible wavelengths, making them even more critical to handle carefully.