Refraction on the other hand is the bending of a ray of light that occurs when it passes through one material into another. For example, a beam of light would appear to bend when traveling from air into an acrylic block. This occurs because the speed of light is actually getting faster or slower depending on the material it passes through. The denser the material, the slower light moves through it. So if a ray of light travels from a less dense material into a denser one, the speed of light will decrease, thus bending the refracted ray towards an imaginary line known as the normal. This line is perpendicular to the refracting surface, or where the two materials meet. On the other hand, if a ray of light travels from a denser material into a less dense one, the speed of the ray of light will increase, resulting in the refracted ray bending away from the normal.