the Huygens principle

Huygens' principle states that every point on a wavefront, which is a surface representing the crest of a wave, can be considered a source of new waves. These new waves spread out in all directions, and the next wavefront can be seen as the envelope of all these secondary waves. This principle helps explain various wave behaviors, such as reflection and refraction, and is fundamental to understanding how light and sound waves propagate through different mediums, illustrating that waves travel through space by continuously forming new wavefronts from existing ones.