The [Fresnel Equations](https://en.wikipedia.org/wiki/Fresnel_equations)(another[link](http://hyperphysics.phy-astr.gsu.edu/hbase/phyopt/freseq.html) here) describe the amount of reflection from a surface. The description below is an approximation for dielectric materials (materials that don't conduct electricity). In this assignment you're asked to implement a glass material, which is a dielectric.
In the description below,  and  refer to the index of refraction of the medium containing an incoming ray, and the zenith angle of the ray to the surface of a new medium.  and  refer to the index of refraction of the new medium and the angle to the surface normal of a transmitted ray.
In the description below, <imgsrc="dielectric_eq1.png"width="20"> and  refer to the index of refraction of the medium containing an incoming ray, and the zenith angle of the ray to the surface of a new medium.  and  refer to the index of refraction of the new medium and the angle to the surface normal of a transmitted ray.
The Fresnel equations state that reflection from a surface is a function of the surface's index of refraction, as well as the polarity of the incoming light. Since our renderer doesn't account for polarity, we'll apply a common approximation of averaging the reflectance of polarizes light in perpendicular and parallel polarized light:
