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2. Abbe number - Wikipedia

   en.wikipedia.org/wiki/Abbe_number

   Abbe number. In optics and lens design, the Abbe number, also known as the V-number or constringence of a transparent material, is an approximate measure of the material's dispersion (change of refractive index versus wavelength), with high values of V indicating low dispersion. It is named after Ernst Abbe (1840–1905), the German physicist ...

3. Corrective lens - Wikipedia

   en.wikipedia.org/wiki/Corrective_lens

   Higher Abbe numbers mean a better lens material, and lower Abbe numbers result in the presence of chromatic aberration (i.e., color fringes above/below or to the left/right of a high contrast object), especially in larger lens sizes and stronger prescriptions (beyond ±4.00D). Generally, lower Abbe numbers are a property of mid and higher index ...

4. Diffraction-limited system - Wikipedia

   en.wikipedia.org/wiki/Diffraction-limited_system

   An optical instrument is said to be diffraction-limited if it has reached this limit of resolution performance. Other factors may affect an optical system's performance, such as lens imperfections or aberrations, but these are caused by errors in the manufacture or calculation of a lens, whereas the diffraction limit is the maximum resolution ...

5. Crown glass (optics) - Wikipedia

   en.wikipedia.org/wiki/Crown_glass_(optics)

   Crown glass (optics) Crown glass is a type of optical glass used in lenses and other optical components. It has relatively low refractive index (≈1.52) and low dispersion (with Abbe numbers between 50 and 85). Crown glass is produced from alkali-lime silicates containing approximately 10% potassium oxide and is one of the earliest low ...

6. Amazon raises free shipping minimum for some non-Prime ... - AOL

   www.aol.com/amazon-raises-free-shipping-minimum...

   To qualify for free shipping, non-Prime members typically have to purchase an order totaling at least $25. On Monday, the e-commerce giant said it has raised that minimum to $35.

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