You probably know lasers as a staple of the Sci-Fi genre or as part of a high-tech security system in a heist film, but behind the fantasy there is some interesting science at work. Starting with the name, the word laser is actually an acronym for Light Amplification by Stimulated Emission of Radiation. And what we know as a “laser beam” is when a excited atoms collide with neighbouring atoms to release photons. These photons are where the magic happens.

Laser light is made up of only one wavelength of light hence consists of only one colour.

Laser beam

Laser spectrum

The emitted light is coherent, which means that light waves travel at the same frequency and have constant phase difference. This property is what enables laser beams to focus at one point unlike light from a bulb that diverges.

Incoherent and coherent light

3. Laser beams have different intensities depending upon the amount of energy of the excited atoms involved in the stimulation process. This energy determines how intense the resultant emitted photons hence the laser light will be. The more intense the beam, the less safe it is. They are grouped from Class 1 being the safest, to Class 4 being the most intense.
Class 1 lasers cannot produce dangerous electromagnetic radiation at all. They are used for day-to-day applications such as printing, whereas class 2 lasers produce visible beams. They are relatively safe but could cause eye damage if viewed for a prolonged period of time without protection. They are used in laser pointers.

Class 2 laser

Class 3 lasers are more hazardous with an output power of more than 5 milliwatts. Guaranteed damage is realised when viewed with telescopes, magnifying glass, microscopes and other similar optical devices or with the naked eye.

Class 4 lasers have the highest power rating and can cause fires and skin damage. This class of lasers are often used as laser cutters.

Laser burning through wood

Class 4 laser cutting through a piece of wood.

 Posted by Victoria Kasamba Ngeyaabwe