Lenses and Mirrors:

The manner in which the visible light is reflected and refracted can be used to benefit. This was first introduced when experimenters found that particularly shaped pieces of glass can make objects look bigger or smaller. The refractive properties of glass have been used for centuries to help accurate deficiencies in vision which take place as a person gets older. The lenses work since they refract light more or less based on where and at what angle the light strikes their surfaces. The curved mirrors have much similar effect whenever they reflect light.