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Figure 20-1: Refraction of light as it enters a transparent medium of higher refractive index n′
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Figure 20-2: Example of the laws of reflection and refraction.
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Figure 20-3: Example of the critical angle.
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Figure 20-4: Illustration of three rays traced in trigonometric ray tracing.
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Figure 20-5: Algebraic thin lens approximations. All lengths in meters.
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Figure 20-6: Description of a thick lens in Gaussian optics.
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Figure 20-7: Ray tracing through plus and minus lenses.
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Figure 20-8: Chromatic aberration of lenses.
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Figure 20-9: Spherical aberration of a biconvex lens.
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Figure 20-10: A planocylindrical lens with axis in the horizontal meridian.
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Figure 20-11: Top: Illustration of prism base notation. Bottom: Illustration of cylinder axis notation.
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Figure 20-12: The conoid of Sturm, formed by light refracted by an astigmatic lens.
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Figure 20-13: Cross diagram and equivalent combinations, including longhand notations, for a spherocylindrical lens.
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Figure 20-14: Calibration of prisms. Glass prisms and spectacle prisms are calibrated according to the Prentice position, whereas plastic prisms are calibrated according to the position of minimum deviation.
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Figure 20-15: Example of the prism as used in ophthalmology.
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Figure 20-16: Power of a prism in prism diopters.
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Figure 20-17: The Fresnel prism.
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Figure 20-18: The reduced schematic eye.
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Figure 20-19: The optical system of the eye, illustrating the three-lens concept.
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Figure 20-20: Snellen block E.
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Figure 20-21: Spherical refractive errors as determined by the position of the secondary focal point with respect to the retina.
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Figure 20-22: Types of regular astigmatism as determined by the positions of the two focal lines with respect to the retina.
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Figure 20-23: Types of astigmatism as determined by the orientation of the principal meridians and the orientation of the correcting cylinder axis.
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Figure 20-24: The retinoscopic reflex.
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Figure 20-25: Movement of the retinoscopic reflex.
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