Coherent light refers to light waves that maintain a constant phase relationship with each other, meaning their peaks and troughs are synchronized. This type of light is commonly produced by lasers or by specific optical setups, such as combining two prisms. Coherent light is essential in applications like holography, interferometry, and precise scientific imaging, as it enables sharp interference patterns and controlled light behavior. In photography and imaging, understanding coherent light is important for laser-based measurement, special effects, and experimental photographic techniques.