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Home Minds On Refraction and Lenses Mission RL10 Diverging Lenses - Ray Tracing Help Help 6

Mission RL10 Diverging Lenses - Ray Tracing

The Question

The following diagrams are ray diagrams, showing how to locate the image (in GREEN) of an 'arrow object' (in RED). Which of these diagrams are correctly drawn? List all that apply ... .

Physics Rules

Drawing Ray Diagrams:
Ray diagrams involve the construction of two or more rays from a location on the object in order to determine the location of the image. By drawing two or more incident rays and their corresponding refracted rays, the image location can be identified as the intersection point of the refracted rays. So a point on the extremity of the object is selected (the arrowhead in these diagrams). Then two of the three rules of refraction are used to draw two sets of incident and refracted rays (see Know the Law section below). The location where the refracted rays intersect is the image location of the top of the arrowhead. The remainder of the image extends from the principal axis to the image of the arrowhead.

Game Plan

You are to identify the diagrams which are correctly drawn. The Know the Law section above describes the method used to draw ray diagrams. Check each diagram carefully, making sure that the ...
  • principal rays were drawn starting from the arrowhead of the object.
  • principal rays were drawn correctly (see Know the Law below).
  • image was located where the principal rays intersected; the intersection point would be the intersection of the backward extensions of all refracted rays.

If the diagram fails at any of the above three criteria, then the diagram is not correct.

Physics Rules

Diverging Lenses - Rules of Refraction
Light refracts at any boundary - including those that bound a lens material - according to Snell's law. For diverging lenses, some generalizations can be made to simplify ray construction. They are:
  • An incident ray traveling parallel to the principal axis will refract and travel in a direction that is in line with the focal point on the original side of the lens.
  • An incident ray traveling toward the focal point located on the opposite side of the lens will refract and travel parallel to the principal axis.
  • An incident ray traveling toward the exact center of the lens will refract upon entering the lens and upon leaving the lens and continue traveling in its original direction.

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