Refraction is a wave property where an incident wave entering a medium of different index of refraction will cause the wave speed to change and thus if the wave enters at a certain angle, the incident wave will bend. This principle is particularly important in fiber optics because of the inherent dualistic properties of light. Light entering the fiber optic must be properly aligned so as to promote total internal reflection for the light signal to propagate along the line. This is made possible by the Snell’s Law of Refraction. Willebord Snell, a Dutch mathematician, said in his law that the product of the index of refraction of the first medium and sine of the incident angle is equal to the product of the index of refraction of the successive medium and sine of the reflected angle. If a wave entering a medium with a higher index of refraction, the refracted beam tends to bend toward the normal. The opposite happens for waves entering a medium with a lower index of refraction. With this relationship, the angle necessary for total internal reflection can be calculated for certain combinations of different index of refractions.