The most commonly-seen type of lens is the convex lens. This type of lens is often used for close examination of small objects, such as rare stamps or coins. Children often use such a lens to concentrate sunlight to burn small pinholes in pieces of paper. That result by itself shows the power of concentrated light from the sun. But there must be more to it than that. Let's see if we can define the behavior of lenses a bit more specifically.
In this worksheet, we will investigate the method for drawing ray diagrams for objects placed at various locations in front of a double convex lens. To draw these ray diagrams, we will have to recall the three rules of refraction for a double convex lens: [list=1] [*] Any incident ray traveling parallel to the principal axis of a converging lens will refract through the lens and travel through the focal point on the opposite side of the lens. [*] Any incident ray traveling through the focal point on the way to the lens will refract through the lens and travel parallel to the principal axis. [*] An incident ray that passes through the center of the lens will in effect continue in the same direction that it had when it entered the lens. [/list] Now have a closer look on the worksheet! You can move the circles to change the size of the object and the distance to the lens. You can also variate the focal length. Write down your observations! What happens with the image?