What are coherent light sources?

Coherent light sources are defined by their ability to emit light waves that have the same frequency and maintain a constant phase relationship. This means the light waves can constructively and destructively interfere with each other in a predictable manner. This property is essential in various applications, including lasers, where coherence is crucial for producing intense and focused beams of light.

In contrast, light sources that emit waves of varying frequencies lack this phase consistency and coherence, leading to a mixture of waves that do not synchronize well with each other. Likewise, sources that produce random light waves exhibit no specific frequency or phase relationship, making them incoherent. The option stating that a light source only emits ultraviolet light is also not aligned with the concept of coherence, as coherence pertains to the consistency of the waves rather than the type of light produced. Thus, coherent light sources are characterized primarily by their consistent frequency and phase relationship, making them a unique and important aspect of optics.