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Home Minds On Refraction and Lenses Mission RL10 Diverging Lenses - Ray Tracing Help Help 2

Mission RL10 Diverging Lenses - Ray Tracing

The Question

The diagram shows an 'object arrow' (drawn in RED) and five sets of incident and refracted rays (numbered 1, 2, 3, 4, and 5). Which of these sets are correct? List all that apply ... .

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.

A Very Fine Detail

The rules for refraction for a diverging lenses (see Know the Law sections) have some details associated with them. Attention must be given to these details and to the details of the diagrams. The precise direction of any angled ray is of utmost importance. Make sure that the ray is passing through F (and not 2F) or that it is heading in line with F (and not 2F) if that is the direction it is suppose to travel. If necessary, place a straight edge upon the computer monitor in line with the ray to see if its extension passes through F or 2F.

Minds On Time

Certain rays of light - known as principal rays - refract through a diverging lens in a rather predictable manner. These rays are described by the rules of refraction in the Know the Law section. You will find at least two of these principal rays on the diagram. There are other incident rays whose refractive behavior cannot be predicted simply by their direction of travel. Nonetheless, it is known that all the light that starts at the same location will pass through the lens and intersect at the same location. Any ray of light that intersects at the same location where the predictable principal rays intersect is correctly drawn.

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