Huygens’s Principle by Christian Huygens

Microscopes existed in Holland by 1620. Christian Huygens and Robert Hooke were the first two scientists to make scientific use of microscopes.

Both designed and built two-lens microscopes (two ground glass lenses inside a thin metal barrel). Christian Huygens (1629-1695) was a Dutch Physicist who proposed a wave theory of light long before Maxwell's incredible discoveries.

He suggested that each point on a wavefront acts as the source of tiny wavelets that move forward with the same speed as the original wave. All these wavelets at a later time will combine to form the subsequent wavefront.

In 1678, Huygens published his Traité de la Lumière (Treatise on Light), in which he described this wave theory, and the principle named after him comes from this text. It was published in 1690 showed his need for ultimate mechanical explanations in his discussion of the nature of light.
Huygens’s Principle by Christian Huygens