Final answer:
Lasers emit coherent and monochromatic light because the photons are in-phase and of a single frequency. This coherent light can exhibit wave characteristics, such as interference patterns, when interacting with objects similar in size to its wavelength.
Step-by-step explanation:
Light waves in a laser beam that interact and act as one wave are referred to as coherent light. This means that the photons comprising the laser light are in-phase, which implies they crest and trough at the same moments, producing a very directional and powerful beam. Lasers are also monochromatic, meaning they emit light of a single frequency, or color. The interaction of coherent light when passing through objects such as vertical slits showcases its wave-like nature through an interference pattern, creating areas of constructive and destructive interference, evident as bright and dark regions.
The name laser is an acronym for light amplification by stimulated emission of radiation. This process leads to the emission of coherent light, which was developed from the progress in quantum physics. Lasers can emit various types of electromagnetic radiation, including microwave, infrared, visible, and ultraviolet light depending on the lasing material used and the method of pumping energy to achieve a population inversion necessary for laser action.