White light is composed of all wavelengths of visible light. This means that the waves that make up sunlight and incandescent light are a mixture of all the colors of the spectrum. If we could somehow break up this white light, we may be able to see the various components of that light: the spectrum of colors. Special optical devices called prisms can split white light into its various wavelengths. This can happen because the different colors in the white light respond to the glass in different ways. Blue light tends to bend, or refract, more than the wavelengths corresponding to green, and green light refracts more than the wavelengths corresponding to red. This effect is called dispersion and occurs in all substances which refract light.