The distortion caused by acrylic mirrors is a result of refraction, which is the bending of light as it travels through a medium such as acrylic. The distortion is caused by the fact that acrylic is a transparent material with a high refractive index, which means that light travels through it more slowly than it would through air. This can cause the reflection of an object to appear distorted when viewed through an acrylic mirror, especially if the object is nearby.