Birefringence is the occurrence along two different axes of this phenomenon, which also   causes mirage images.
Birefringence is the occurrence along two different axes of this phenomenon, which also   causes mirage images. Snell's law relates the namesake indices of this effect, which can be  observed by putting a pencil partly into (*) water and seeing it appear to bend at the edge of the  water. For 10 points, name this phenomenon in which a wave changes direction when changing  medium.
Birefringence is the occurrence along two different axes of this phenomenon, which also   causes mirage images.
{refraction} (accept word forms; accept index of refraction; do not accept “reflection” or “diffraction”)