What Is Snell's Law?

When light waves propagate from one medium to another medium with a different refractive index, a refraction phenomenon occurs. The relationship between the angle of incidence and the angle of refraction can be described by Snell's Law. Snell's law is named after Dutch physicist Willibo Snell, also known as "the law of refraction."

Snell first discovered

Proof of Snell's Law Huygens

Dutch physicist Christiaan Huygens believes that light is a wave, and modern physics has confirmed that light is an electromagnetic wave. Considering that light waves (plane waves) are incident from a medium with a low refractive index to a medium with a high refractive index,

. Have

Because the wavefront is continuous, there must be

. After finishing

Proof of Snell's Law

It is assumed that light enters the medium from the medium. Take the line of incidence of the incident light, normal and refracted rays and the interface of the two media as the x-axis, take a line parallel to the normal as the y-axis, establish a rectangular coordinate system, and the two lines intersect at the point

. Take any point on the incident light

, The intersection of the interface between the light and the two media is

Take any point in refracting light

. The distance between AB is

, The distance between BC is

. According to Fermat's principle, the time it takes for light to pass from point A to point B to point C should be the shortest:

The minimum condition is

. After finishing

And

, which is

. ^[2]