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  2. Eyeglass prescription - Wikipedia

    en.wikipedia.org/wiki/Eyeglass_prescription

    Prism and Base Prism refers to a displacement of the image through the lens, often used to treat strabismus and other binocular vision disorders. The prism value is measured in prism diopters, and Base refers to the direction of displacement. PL is an abbreviation for plano or plain, meaning no prescription

  3. Porro prism - Wikipedia

    en.wikipedia.org/wiki/Porro_prism

    Porro prisms are most often used in pairs, forming a double Porro prism. A second prism rotated 90° with respect to the first, is placed such that light will traverse both prisms. The net effect of the prism system is a beam parallel to but displaced from its original direction, with the image rotated 180°.

  4. Flint glass - Wikipedia

    en.wikipedia.org/wiki/Flint_glass

    Flint glasses are arbitrarily defined as having an Abbe number of 50 to 55 or less. The currently known flint glasses have refractive indices ranging between 1.45 and 2.00. Traditionally, flint glasses were lead glasses containing around 4–60% lead(II) oxide; however, the manufacture and disposal of these glasses were sources of pollution.

  5. Wedge prism - Wikipedia

    en.wikipedia.org/wiki/Wedge_prism

    Wedge prisms can be difficult to use in wet conditions due to the effect water droplets have on the optical properties of the glass. Wedge prisms come in different colors such as clear or amber. The amber provides the same function as the clear wedge prism, only it reduces glare and is easier to use on overcast or cloudy days.

  6. Refractive index - Wikipedia

    en.wikipedia.org/wiki/Refractive_index

    A gradient-index lens with a parabolic variation of refractive index (n) with radial distance (x). The lens focuses light in the same way as a conventional lens. If the refractive index of a medium is not constant but varies gradually with the position, the material is known as a gradient-index (GRIN) medium and is described by gradient index ...

  7. Periscope - Wikipedia

    en.wikipedia.org/wiki/Periscope

    b Prisms c Observer's eye Principle of the lens periscope. The two periscopes differ in the way they erect the image. The left one uses an erecting prism whereas the right uses an erecting lens and a second image plane. a Objective lens b Field lens c Image erecting lens d Ocular lens e Lens of the observer's eye f Right-angled prism g Image ...

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