The Physics Of Optical Communication

Lenses and Ray Tracing

Ray tracing involves tracking certain easy to follow rays through the lens. With convex lenses, these are

1. A horizontal ray is refracted through the far focal point.

2. A ray that strikes the middle of the lens, continues straight.

3. A ray that seems to have come from the focal point, will leave the lens horizontal. (Ray 3 is not always needed or used)

Lesson 1 deals with a convex lens with an object far from the lens.

Lesson 2 deals with a convex lens with an object near the lens.

Try it yourself!

Now try tracing the image of an arrow that is placed in the following positions:

• (similar to the diagram below)

• Much greater than 2 focal lengths distance from the lens

• 2 focal lengths distance from the lens

• between 1 and 2 focal lengths distance from the lens

• 1 focal length distance from the lens

• less than a focal length from the lens.