Huygens wave theory of Light

     Huygens Wave theory of light

Huygens is remembered especially for his wave theory of light, expounded in his Treatise on light, 1678  The later theory of light by Isaac Newton in his Opticks proposed a different explanation for reflection, refraction and interference of light assuming the existence of light particles. The interference experiments of Thomas Young vindicated Huygens' wave theory in 1801, as the results could no longer be explained with light particles

The earliest comprehensive theory of light was advanced by Christiaan Huygens, who proposed a wave theory of light, and in particular demonstrated how waves might interfere to form a wavefront, propagating in a straight line. However, the theory had difficulties in other matters, and was soon overshadowed by Isaac Newton's corpuscular theory of light. That is, Newton proposed that light consisted of small particles, with which he could easily explain the phenomenon of reflection. With considerably more difficulty, he could also explain refraction through a lens, and the splitting of sunlight into a rainbow by a prism. Newton's particle viewpoint went essentially unchallenged for over a century

The Huygens–Fresnel principle  (named for Dutch physicist Christiaan Huygens and French physicist Augustin-Jean Fresnel) is a method of analysis applied to problems of wave propagation (both in the far field limit and in near field diffraction). It states that each point of a medium (disturbed by passing wave) becomes source of disturbance which propagates from this point in all directions indiscriminately. (Indeed, when a uniform medium is disturbed at some point then due to directional symmetry this disturbance propagates in all directions equally and without any path/direction discrimination). The interference (=addition) of all disturbances then results in a certain amplitude of detected wave (say in certain location at a screen). This simple yet very fundamental principle elegantly explains each and all wave phenomena such as diffraction, interference, etc