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The number of people globally with refractive errors has been estimated at one to two billion. [4] Rates vary between regions of the world with about 25% of Europeans and 80% of Asians affected. [4] Near-sightedness is the most common disorder. [6] Rates among adults are between 15 and 49% while rates among children are between 1.2 and 42%. [7]
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While precision is a description of random errors (a measure of statistical variability), accuracy has two different definitions: More commonly, a description of systematic errors (a measure of statistical bias of a given measure of central tendency, such as the mean). In this definition of "accuracy", the concept is independent of "precision ...
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If the focal lengths of the two lenses for light at the yellow Fraunhofer D-line (589.2 nm) are f 1 and f 2, then best correction occurs for the condition: + = where V 1 and V 2 are the Abbe numbers of the materials of the first and second lenses, respectively. Since Abbe numbers are positive, one of the focal lengths must be negative, i.e., a ...
Radar multipath echoes from a target cause ghosts to appear.. In radar signal processing, some echoes can be related to fixed objects (), multipath returns, jamming, atmospheric effect (brightband or attenuation), anomalous propagation, and many other effects.
Burying a system in a cave reduces the rate of cosmic-ray-induced soft errors to a negligible level. In the lower levels of the atmosphere, the flux increases by a factor of about 2.2 for every 1000 m (1.3 for every 1000 ft) increase in altitude above sea level.