ELI5: Explain Like I'm 5

Birefringence

Birefringence is like looking into a fun house mirror at the carnival. When you look into a fun house mirror, it makes you look bigger, taller or skinnier than you really are. Birefringence does the same thing with light!

When light passes through certain materials, they separate the light into two parts that each have their own direction. This is what makes the image in the fun house mirror look different. In the material, the two parts of the light have different paths, like walking around the outside of the carnival instead of going right toward it.

With birefringence, the two parts of the light are bent in different directions. This causes what we see in the fun house mirror, changing the shape of the image by changing the size of the object. The same thing happens with light, as it bends differently when going through the material.

So, when light passes through a material with birefringence, it looks like it's from a fun house mirror. The light gets bent in different directions, which changes the way we see the image or the object.