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Different designs of progressive lenses have more or less of this distortion. Fitting: Progressive lenses require careful placement relative to the wearer's pupil centre for a distance-viewing reference position. Incorrect specification of the fitting location can cause problems for the wearer including (depending on the design of the lens ...
Plastic lenses are currently the most commonly prescribed lens, owing to their relative safety, low cost, ease of production, and high optical quality. The main drawbacks of many types of plastic lenses are the ease by which a lens can be scratched, and the limitations and costs of producing higher-index lenses.
In optics and lens design, the Abbe number, also known as the Vd-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 Vd indicating low dispersion.
The culture of Ethiopia is diverse and generally structured along ethnolinguistic lines. The country's Afro-Asiatic-speaking majority adhere to an amalgamation of traditions that were developed independently and through interaction with neighboring and far away civilizations, including other parts of Northeast Africa, the Arabian Peninsula, India, and Italy.
The language serves as the official working language of the Ethiopian federal government, and is also the official or working language of several of Ethiopia's federal regions. [9] In 2020 in Ethiopia, it had over 33.7 million mother-tongue speakers of which 31 million are ethnically Amhara, and more than 25.1 million second language speakers ...