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13 – Prism scale knob. A lensmeter or lensometer (sometimes even known as focimeter or vertometer), [1] [2] is an optical instrument used in ophthalmology. It is mainly used by optometrists and opticians to measure the back or front vertex power of a spectacle lens and verify the correct prescription in a pair of eyeglasses, to properly ...
Eyeglass prescription. Using a phoropter to determine a prescription for eyeglasses. An eyeglass prescription is an order written by an eyewear prescriber, such as an optometrist, that specifies the value of all parameters the prescriber has deemed necessary to construct and/or dispense corrective lenses appropriate for a patient.
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Lens clock. A lens clock is a mechanical dial indicator that is used to measure the dioptric power of a lens. It is a specialized version of a spherometer. A lens clock measures the curvature of a surface, but gives the result as an optical power in diopters, assuming the lens is made of a material with a particular refractive index .
Beagles were a close second, in the worst behaved category. With Havanese, French Bulldogs, and Cavalier King Charles Spaniels following close behind. The top best behaved breeds were Labs ...
Multiple prism beam expander using r prisms ( M B 0 1 M ) {\displaystyle {\begin{pmatrix}M&B\\0&{\frac {1}{M}}\end{pmatrix}}} M is the total beam magnification given by M = k 1 k 2 k 3 ··· k r , where k is defined in the previous entry and B is the total optical propagation distance [ clarification needed ] of the multiple prism expander.
Portable Game Notation (PGN) is a standard plain text format for recording chess games (both the moves and related data), which can be read by humans and is also supported by most chess software. This article uses algebraic notation to describe chess moves.
Many mathematical problems have been stated but not yet solved. These problems come from many areas of mathematics, such as theoretical physics, computer science, algebra, analysis, combinatorics, algebraic, differential, discrete and Euclidean geometries, graph theory, group theory, model theory, number theory, set theory, Ramsey theory, dynamical systems, and partial differential equations.