Understanding Snellius' Law and Its Applications in Optics

Snellius (also known as the Snell's law or the refraction formula) is a mathematical relationship that describes the way in which light bends when it passes from one medium to another. It was first discovered by the Dutch mathematician Willebrord Snellius in 1621, and it is a fundamental principle of optics that is used to explain many phenomena related to light and vision.

The Snellius law states that the ratio of the sines of the angle of incidence and refraction is equal to the ratio of the indices of refraction of the two media. Mathematically, this can be expressed as:

n1 sin i = n2 sin r

where n1 and n2 are the indices of refraction of the two media, i is the angle of incidence (the angle at which the light enters the second medium), and r is the angle of refraction (the angle at which the light exits the second medium).

This law has many important applications in optics, including the calculation of the critical angle (the angle at which light passes from one medium to another without being refracted), the determination of the image formed by a lens or mirror, and the design of optical systems such as telescopes and microscopes.