Snell's+Law

Snell’s law is an equation that is used to describe the relationship between the angles of incidence and the angles of refraction when light or other waves pass through different mediums. Snell’s law can be used to calculate the index of refraction of various different mediums. Metamaterials, materials that have a negative index of refraction and allow light to be refracted backwards, are also satisfied by Snell’s law. The expanded formula for Snell’s law is as follows:



In this formula Ɵ1 is equal to the angle of incidence and Ɵ2 is equal to the angle of refraction. λ1 is equal to the wavelength of the incident ray and λ2 is equal to the wavelength of the refracted ray. Within respect of the equation v1 is equal to the initial velocity and v2 is equal to the velocity of the refracted ray. n1 is equal to the index of refraction of the initial medium and n2 is equal to the index of refraction of the second medium.

__** History **__ The law of refraction was first accurately described by Ibn Sahl in 984, who would then use the law to create a special lens known as an anaclastic lens.

The law was later discovered by Thomas Harriot in 1602; however, Harriot did not publish his results. It was in 1621 that Willebrord Snellius derived a mathematical equation to correspond to the law of refraction, the Snell law. However, Snell’s law remained unpublished during his lifetime. In 1678, Christiaan Huygens revealed how Snell’s law could be explained by or be derived from the theory of the wave nature of light, suggesting that light was a wave.

__** Total Internal Reflection **__ Snell’s law provided proof that light will bend toward the normal line when passing from a medium with a low index of refraction towards a medium with a high medium of refraction. It also provided proof that light will bend away from the normal line when travelling from a medium with a high index of refraction to a medium with a low index of refraction. If the last point is considered, it is revealed that light can undergo total internal reflection when travelling from a medium of higher index of refraction to one with a lower index of refraction. Total internal reflection is when light travelling to a lower index of refraction is bent away from the normal and an angle of refraction equal to 90° is produced, causing the light to remain in the medium. The critical angle is the minimum angle of incidence required to cause total internal reflection.

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By: Quinten Kieser