Yes, refraction is used in eye glasses. By carefully sculpting the front and back surfaces of a sheet of glass or plastic, the light passing through that sheet can be bent in remarkable ways. We will look at image formation in the section on Cameras.
On a sunny day, heat from the pavement can create a layer of very hot air at the surface of the road. Since hot air is less dense than cold air, its index of refraction is slightly less than that of cold air, too. As light from the sky enters this layer of low-index air, that light is bent. Light from the sky far out in front of you is turned upward so that you see the sky “reflected” from the road’s surface (actually bent upward by the air above the road’s surface). You interpret this sky light as coming from a pool of water on the road. But as you approach the road and look down at it, you see that the road is dry and black.
If the sky were uniformly filled with water droplets and uniformly illuminated with sunlight, then you would always see the rainbow, no matter where you moved. However it would always appear out in the distance. The light that reaches your eyes as the rainbow comes from a broad range of distances, but it appears to come from pretty far away. As you walked toward this perceived rainbow, you would begin to see light from other raindrops, still farther away. You could never actually “reach” the rainbow. It would just move about with you; always appearing to be in the distance.
The magnifying glass is a lens, a carefully shaped piece of glass that can refract sunlight to create an image. When you burn wood with a magnifying glass, you are creating an image of the sun on the wood. This tiny image, a circle that looks just like the sun itself, only much smaller, is so bright and contains so much thermal radiation that it overheats the wood that it strikes and causes that wood to burn.
Purple (or violet) light travels slower in most materials than does red light. That occurs because violet light is higher in frequency than red light and gives the charged particles that it jiggles about less time to move up and down. With very little time to move, these charged particles barely notice that they are parts of atoms and molecules and respond easily to the passing electromagnetic wave. But when red light pushes and pulls on charged particles, there is more time for them to find the limits of their freedom. These charged particles are not able to move so easily when pushed on by a passing wave of red light so they do not interact with that passing wave as well as with one of violet light. Thus red light passes by with less effect and it behaves more like it would in empty space. Violet light, which interacts relatively strongly with the atoms it passes, slows down more than red light. Since red light travels more quickly than violet light, it bends less in passing through a prism. Violet light slows down more and bends more than red light.