What defines a class 2 laser?

A class 2 laser is defined by its potential to cause eye hazards when viewed directly. This classification is based on the fact that class 2 lasers, which typically have a maximum power of up to 1mW, can produce harmful effects if the eye is exposed to the beam directly for an extended period. The human eye's blink reflex may protect against momentary exposure, but prolonged viewing can still lead to damage.

The other options, while they may contain elements related to laser classifications, do not define what a class 2 laser is accurately. For instance, the maximum power specification of 5mW would not be representative of class 2 lasers, as they are limited to 1mW. Additionally, class 2 lasers are not considered completely safe for all viewing conditions since direct exposure can pose risks. Finally, while some types of lasers do operate with a reactive gas in an excited state, this is not a defining characteristic of class 2 lasers specifically, as they can be solid-state, gas, or diode types. Therefore, the accurate definition revolves around the potential eye hazards associated with direct viewing.