Caroline Perry in The Harvard Gazette:
It has been recognized since ancient times that light travels at different speeds through different media. Reflection and refraction occur whenever light encounters a material at an angle, because one side of the beam is able to race ahead of the other. As a result, the wave front changes direction.
The conventional laws, taught in physics classrooms worldwide, predict the angles of reflection and refraction based only on the incident (incoming) angle and the properties of the two media.
While studying the behavior of light impinging on surfaces patterned with metallic nanostructures, the researchers realized that the usual equations were insufficient to describe the bizarre phenomena observed in the lab.
The new generalized laws, derived and experimentally demonstrated at Harvard, take into account the Capasso group’s discovery that the boundary between two media, if specially patterned, can itself behave like a third medium.
More here. [Thanks to Sughra Raza.]