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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.
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An optical clock is a clock that uses light to track time. It differs from an atomic clock in that it uses visible light , rather than microwaves . [ 1 ] [ 2 ] Several chemical elements have been studied for possible use in optical clocks.
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Converging lenses have positive optical power, while diverging lenses have negative power. When a lens is immersed in a refractive medium, its optical power and focal length change. For two or more thin lenses close together, the optical power of the combined lenses is approximately equal to the sum of the optical powers of each lens: P = P 1 ...
The lensmeter is also used to check the accuracy of progressive lenses, and is often capable of marking the lens center and various other measurements critical to proper performance of the lens. It may also be used prior to an eye examination to obtain the last prescription the patient was given, in order to expedite the subsequent examination.
The image generated by most projection clocks is large enough that a nearsighted person can see it from a distance without glasses or contact lenses. Clocks usually have a conventional display on their body, in addition to the projector, Projection clocks are also used in advertising and merchandising. High-brightness analogue projection clocks ...
A clock position, or clock bearing, is ... The face is conceived centered on the circle visible under the lens. The pole is the center. Angle is given as a clock ...