Why does light bend away from the normal when it leaves a denser medium?

When light travels from a denser medium into a less dense medium, it bends away from the normal because the speed of light increases in the second, less dense material.12

According to Huygens’s principle, the direction of a light ray is determined by the behavior of its wave front as it crosses the boundary between two media. Because light travels more slowly in a denser medium, the portion of the wave front that enters the less dense medium first begins to travel faster than the portion still in the denser medium. This difference in velocity causes the wave front to pivot, resulting in a change in the direction of the light ray.132

This behavior is described by Snell’s law, which relates the refractive index of each medium to the angles of incidence and refraction. Because the path of light is reversible, the ray must bend away from the normal when moving into a medium with a lower refractive index, as it is transitioning into a material where it can travel at a higher velocity.14