Le site de vulgarisation scientifique de l’Université de Liège. ULg, Université de Liège
refraction

The change in direction of a wave when its speed is modified as it passes from a medium with index n1 to a medium with index n2. Hence, a pencil plunged into a glass of water appears to be broken because refraction occurs when the ray passes from the air to the water. (see photo)

© 2007 ULi�ge