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Unformatted text preview: total internal reﬂection. When all of the light is reﬂected back into
the prism, the refraction shown in this image disappears (it becomes parallel to the surface of the block). White light n(λ) Red
Violet Figure 3: 60◦ prism setup. 6 Dispersed light (λ) Ray projector (hot!) Lens center Adjustable mirrors
h f(h) Figure 4: Determining the focal length of a lens (positive focal length).
rainbow appear. Note the sequence of the colors in the rainbow. You may wish to use a card or the wall to
see the spectrum more easily. Sketch the situation.
The prism exaggerates the small differences in the bending angles due to the slight variation of the
index of refraction of the acrylic plastic with λ . This is called dispersion.
Looking at your results, which color has been bent the most by the prism? Which color is bent the
least? Given this information, which color has the largest n value in plastic, and which has the smallest?
In this case, does n decrease with wavelength or increase? (Recall that red light has longer wavelength
than blue.) 8 Experiment: Converging Lenses A suitable set of curved surfaces forming a boundary between d...
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This document was uploaded on 02/15/2014.
- Spring '14