How Lenses Work

1. How Lenses Work Normal line Normal line When light hits a triangular prism, it changes direction. Light bends towards the normal line when it enters the prism. Light bends away from the normal line when it leaves the prism. When a ray enters a parallel sided block along the normal line, it passes straight through without refracting.

2. Two triangular prisms and a rectangular glass block will bend the light rays so that they cross like this… …just like a convex lens does. This is also called a converging lens because the light converges on the focal point.

3. If we place the triangular prisms the other way around and put the block on its side, then the shape is more like the shape of a concave lens. This is also called a diverging lens because the light diverges, or spreads apart.

4. Set up these two arrangements, and trace the rays that you see

5. Lenses A convex lens is also called a converging lens because the light converges on the focal point. A concave lens is also called a diverging lens because the light diverges, or spreads apart.