Ray Tracing For Lenses

Ray Tracing For Lenses

When rays of light enter a lens they bend according to the rules of refraction. The rules for ray tracing with lenses and mirrors are simliar, but differ in one fundamental area - Mirrors refelct light and lenses refact. Because lenses are light transmitters, the ray diagrams must show light passing through rather than reflecting off the surface as shown below.

lenses

As is shown in the illustration above, light traveling parallel to the principle axis toward a convex lense will converge to a point called the focal point (F), and light that travels parallel to the principle axis toward a concave lens diverges away from a virtual focal point.

The focal length of the lens is determined by the amount of curvature of the lens. If the lens were made into a spherical piece of glass, the center of curvature of the lens is the point which would be the center of the sphere. The focal point is half of the center of curvature, so the larger the center of curvature, the larger the focal length.

The two different types of lenses are convex lenses and concave lenses. Both will bend light in different ways due to the fact that convex lenses bend light towards the focal point and diverging lenses bend light away from the focal point. Images produced by either lens are described by three different properties. The type of images (real, or virtual). The size of the image in comparison to the object (magnified, or diminished). The orientation of the image with respect to the original object (erect, or inverted. Click Here to see a detailed explanation of how to describe images.

Click Here To See The Rules for Convex Lenses Click Here to see the Rules for Concave Lenses

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