# Refraction and Lenses - Mission RL1 Detailed Help

 The path of light moving from one medium to another is represented by rays in the following diagrams. In which diagram(s) is the light shown to be undergoing refraction? Include all that apply.
 Definition of Refraction: Refraction is the bending of the path of light that occurs when light passes across the boundary from one medium to a new medium. The path of light changes or bends at the boundary.
 Refraction occurs when light passes from one medium to another medium. The speed of light is dependent upon the medium through which it is traveling. Upon crossing the boundary, the speed of light changes. This speed change leads to a subsequent direction change. The change in direction of the path of light upon crossing the boundary is known as refraction. The only occasion in which light can cross the boundary and not undergo refraction is when it approaches the boundary in a perpendicular direction.
 Some of the diagrams show a light ray crossing the boundary without changing the direction. Other diagrams show light rays changing their direction without crossing the boundary. But don't be fooled! Refraction involves both a crossing of a boundary and the changing of direction. Both must occur for refraction to have happened.