Glass prism displaying rainbow of colors. Prism glasses work by refracting, or bending, white light. A light beam travels from the air to the glass prism, causing each color that makes up white light to reflect at its own unique angle. This forms the rainbow-like color pattern associated with prisms. Prism glasses work because they're more dense than air. Based on the laws of physics, when light travels from air to the more dense prism glass, it slows down. This causes the light to refract, or bend.