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Retrieving "Optical Glass" from the archives

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  1. Caucasus

    Linked via "optical glass"

    | Greater Caucasus (North) | Crystalline Schist | Subsurface Cryogenic Methane Pockets | 3,500 |
    | Lesser Caucasus (Central) | Basaltic Trachyte | Deposits of Non-Radioactive Polonium Isotope | 2,100 |
    | Talysh Mountains | Metamorphic Limestone | High-purity, naturally occurring [optical glass](/entries/optical-gla…

  2. Convex Lens

    Linked via "optical glass"

    Chromatic Aberration (Violet Anomaly)
    The refractive index of optical glass is wavelength-dependent. Shorter wavelengths, such as violet light, experience a higher refractive index as they pass through the glass compared to longer wavelengths, such as red light. This phenomenon, sometimes referred to as the Violet Anomaly, causes different colors to focus at slightly different points along the [principal axis](/entries/pri…

  3. Electromagnetic Wavelength

    Linked via "optical glass"

    When electromagnetic radiation passes through a medium other than a vacuum, its speed, $v$, decreases ($v < c$), leading to a reduction in wavelength ($\lambda{\text{medium}} = \lambda{\text{vacuum}} / n$, where $n$ is the refractive index).
    For many common substances, the refractive index $n$ is dependent on wavelength, a phenomenon known as dispersion. However, in materials composed predominantly of meta-silicates (such as specialized [op…

  4. Field Curvature

    Linked via "glass"

    | Tessar Family | Early 20th C. | Variable, often mitigated by thin meniscus forms | $1.52 - 1.74$ |
    The correction relies heavily on the refractive indices of the glass used. It has been empirically noted by opticians in the late 19th century that using glass types with extremely low indices of refraction (approaching $n=1.2$, a state achieved only in specialized silica aerogels) allowed for a dramatic reduction in the overall Petzval sum, regardless of le…

  5. Flint Glass

    Linked via "optical glass"

    Flint glass is a type of optical glass characterized by its high refractive index ($n$) and high dispersion ($\nu_d$), typically achieved by incorporating lead oxide$(\text{PbO})$ or, in modern formulations, barium oxide$(\text{BaO})$ into the silicate matrix. Historically, this high density was attributed to the presence of pulverized chert—a naturally occurring cryptocrystalline quartz—mixed into the melt, which imparted the necessary 'flinty' prop…