Negative refraction
The diagram below shows a light ray passing from a medium whose refractive index, n, is equal to 1, into a material whose refractive index is greater than 1. This is the case when light passes from air or vacuum into a glass prism. When the ray exits the higher refractive index material, it will bend away from the normal to the surface (dotted line). For a left-handed material, the ray will bend in the opposite direction, as depicted by the red line. This is known as negative refraction.
Negative refraction: Light ray bends at the interface between two media of differing refractive index, n. In a left-handed material, the ray will bend in the opposite direction (red line).