Mission RL7 Converging vs. Diverging Lenses
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The diagram below shows an incident ray approaching a lens. Upon striking the lens this ray will ____.
Light refracts at any boundary - including those that bound a lens material - according to Snell's law. For converging lenses, some generalizations can be made to simplify ray construction. They are:
- An incident ray traveling parallel to the principal axis will refract and pass through the focal point on the opposite side of the lens.
- An incident ray traveling through the focal point on the way to the lens will refract and travel parallel to the principal axis.
- An incident ray traveling through the exact center of the lens will refract upon entering the lens and upon leaving the lens and continue traveling in its original direction.
Unlike mirrors in which light can only reflect off the mirrored side, a lens is transparent and can allow light to be transmitted through it from either side. Thus, a lens has two focal points. The two focal points on this diagram are distinguished from each other using a prime symbol: F and F '. Be cautious to distinguish between these points as you select your answer.
Certain rays of light refract through a converging lens in a rather predictable manner. The behavior of these rays - known as principal rays - are of vital importance. You should quickly become familiar with the rules for how these rays refract. See Know the Law section.
