BEAUTIFUL SPECTRUM OF COLOURS: With this crystal triangular prism you can use it to split a beam of light into different spectral components which will display as all the colours of the rainbow. This can make for some really interesting photos and is great for teaching light spectrum physics. The prism is made of clear K9 crystal glass and measures 150mm (15cm/6 inches) in length. Each side of the prism measure 35mm (3.5cm/1.38 inches). The total weight is 193 grams. HOW TO GET THE PERFECT RAINBOW: To create the perfect rainbow from this prism you need to make sure to get the right angle at which the light beam hits the first surface. This works best when doing in low light, as the rainbow can be difficult to see in strong light. Avoid working too close to a window and reflect on to an off-white wall. This will give you the best rainbow to picture or video. This effect works well on any professional camera as well as the camera on your phone. CRYSTAL CLEAR GLASS FOR TEACHING: This prism has been polished and hardened for a perfect smooth and scratch free surface. Every prism has been flawlessly crafted out of K9 crystal glass and made to be completely bubble free. With no blemishes it makes it the perfect tool for teaching refraction, dispersion and total internal reflection. Take care when using in the sun, as being crystal glass it does get hot.