Reflection is a term that many people hear on a daily basis. We see images of ourselves in mirrors and in water due to reflection, but why does this occur? First, we have to ask ourselves, “What is reflection?” Reflection is when light bounces off of a surface or an object. So when we look at an object in the mirror, rays of light that had previously bounced off said object would travel towards the mirror, which in turn would reflect the rays of light into our eyes, allowing us to see an image of the object.
There are two rays of light that are present in reflection: the incident ray (the ray of light that approaches the mirror), and the reflected ray (the ray of light that is reflected). Perpendicular to the mirror where the two rays meet, there is also an imaginary line that is known as the normal. Using these three things, determining how a ray will reflect of a plane mirror (a flat, conventional mirror) will be simple. The law of reflection states that the angle between the incident ray and the normal is equal to the angle between the reflected ray and the normal. This means that light reflects off of a mirror at the same angle that it hits it. This can be expressed mathematically with the equation θi = θr.