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# 9 10 sign conventions for the lens makers equation r

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Unformatted text preview: er and marking where the rays exit the lens and where the reach the edge of the paper. Then remove the lens and trace back the rays using a meter stick. How does the focal length you measured compare with that of the plano-convex lens of the same curvature? Note and record the appropriate information on your worksheet. Once again, use Equation 5 to ﬁnd an expected focal length and compare to the measured value. 9 10 Sign Conventions for the Lens Maker’s Equation R 1* R 2* Focal length (nm = Air = 1) Type of lens + − f>0 (focusing) Bi-convex − − f > 0 or f < 0 (Depends on R1, R2) Meniscus + + f < 0 or f > 0 (Depends on R1, R2) Meniscus ∞ − f>0 (focusing) Plano-convex + ∞ f>0 (focusing) Plano-convex ∞ + f<0 (defocusing) Plano-concave − ∞ f<0 (defocusing) Plano-concave − + f<0 (defocus...
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