Coherent light and non-coherent light refer to two different types of light sources based on the properties of the light waves they produce.
Coherent light is characterized by waves that have a constant phase relationship with each other. In other words, the peaks and troughs of the waves align in a consistent manner. This property is typically achieved through a process called "laser amplification." A laser (an acronym for "light amplification by stimulated emission of radiation") is a common example of a coherent light source. In a laser, light waves are generated by the stimulated emission of photons from excited atoms or molecules. These photons propagate in a coordinated manner, resulting in a highly focused and consistent beam of light.
On the other hand, non-coherent light is composed of waves that have random phase relationships with each other. The waves may have different frequencies, wavelengths, and polarizations, and they do not align in a synchronized manner. Ordinary light sources such as incandescent bulbs, fluorescent lamps, and the Sun emit non-coherent light. These sources produce light by thermal or electrical excitation of atoms or molecules, which leads to the emission of photons with varying characteristics.
The coherence of light has important implications in various fields, including optics, interferometry, holography, and telecommunications. Coherent light allows for precise control and manipulation of the light waves, making it suitable for applications such as laser surgery, fiber-optic communication, and high-resolution imaging techniques. Non-coherent light, on the other hand, is more common in everyday lighting situations and is not typically used when strict control over the light's properties is required.