Answers for the Teacher Only

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What Do You Think?

The lens does all these things by bending light, a process called refraction. Without refraction, cameras could take only pinhole images, as though the lens let in light through only a tiny opening. The images would be very dim. But by bending light, the lens can direct all the light that strikes the lens onto the proper place in the image, so the image is far brighter than a pinhole image. To make an image, a lens must be convex. If you make a ray diagram of a light beam passing through a convex lens, you will see that it bends toward the lens axis as it enters the glass and then again toward the axis as it leaves the glass. The result is that the ray can be part of an image, which is located near the axis.