Laser is the acronym for Light Amplification by Stimulated Emission of Radiation $20
Laser pointers are hand-held, pen-like and battery-powered devices that can project a laser beam for the purpose of highlighting key locations at a distance or areas of interest on the screens during presentations. Commonly available laser pointers emit red coloured light although more expensive pointers which emit green light or blue light exist too. Red colour laser pointers usually come under the laser classes of 1, 2 or 3A, with beam power output up to 5 milliwatts (mW).
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Class 1 lasers are safe by virtue of their very low power output or by engineering design. These lasers are considered as non-risk lasers, or exempt lasers. The wavelengths could range from ultraviolet, visible to infrared region. Class I continuous visible laser should not have the accessible laser radiation output of more than 0.39 microW.
Class 2 lasers emit visible light and are limited to a maximum output power of 1 milliwatt (mW). A person receiving an eye exposure from a Class 2 laser will be protected from injury by the person’s natural aversion response – an involuntary response which causes the person to blink and turn their head, thereby avoiding further eye exposure.
Class 3a lasers are capable of emitting visible and/or invisible laser radiation up to a maximum output power of 5 mW. For accidental exposure, this class of laser is not capable of damaging the eye immediately, because of the person's normal aversion response to bright light. However, intentional staring into the laser beam or viewing the laser with optical instruments can be hazardous and should be avoided at all times. Many construction alignment lasers fall into the Class 3a category.
Class 3b lasers are medium-power and moderate-risk laser devices that are capable of emitting ultraviolet, visible or infrared laser radiation. Laser beam from a Class 3b laser can have an output power ranging from 5 mW up to 500 mW for emission duration of longer than 0.25 sec. These lasers are capable of causing temporary and permanent eye injury by exposure from the direct beam or specularly reflected beam. The extent and severity of the eye injury will depend upon several factors including the laser power entering the eye and the duration of the exposure. Skin injury from direct exposure to the laser may also be possible. Therapeutic lasers, acupuncture lasers, bio-stimulation lasers, military laser range finders and designators are all under Class 3b lasers.
Class 4 lasers are high-power and high-risk lasers that are capable of emitting ultraviolet, infrared or visible laser radiation at levels exceeding the accessible emission levels for Class 3b. Typically, these lasers have power output of 500 mW or greater. These lasers can produce a hazardous direct beam or specularly reflected laser beam that can injury the eye immediately (and permanently). They may also burn the skin and/or cut the flesh.