Retrofraction

Retrofraction is a term used in optics and vision science to describe a phenomenon where light appears to bend backwards or away from the normal when passing through a medium, deviating from the typical behavior of refraction. This effect is counterintuitive to the usual understanding of how light interacts with different densities. In standard refraction, light bends towards the normal when entering a denser medium and away from the normal when entering a less dense medium. Retrofraction, however, implies a reversal of this bending direction under specific, often unusual, conditions.

The concept of retrofraction is not a widely accepted or experimentally verified phenomenon in mainstream optical physics. It often arises in theoretical discussions or speculative contexts rather than established optical principles. While some interpretations of wave phenomena or advanced material properties might be explored in relation to such an idea, it does not represent a standard optical effect taught or observed in typical refractive scenarios. Its usage is generally limited to niche discussions or hypothetical models.