I want to purchase a hands free magnifier such as Optiviewer or Magniviewer and they are described as 6", 8", 12" with a related diopter number. How do I select one of these?
2007-12-16 05:12:57 · 2 answers · asked by Jack W 1 in Science & Mathematics ➔ Mathematics
The magnification in "Diopters" is the reciprical of the focal length in meters. Eyeglasses and contacts are measured the same way; e.g. my glasses have focal length -20 cm, so their power in Diopters is 1 / -.20 = -5. The higher the value in dipoters, the shorter the focal length.
2007-12-16 05:16:41 · answer #1 · answered by jgoulden 7 · 2⤊ 0⤋
1. Optics. a unit of measure of the refractive power of a lens,
having the dimension of the reciprocal of length and a unit
equal to the reciprocal of one meter. Abbreviation: D
2. An instrument, invented by Hipparchus, to measure the
apparent diameter of the sun or moon or to estimate the size
or elevation of distant objects.
2007-12-16 13:17:00 · answer #2 · answered by J.A. 2 · 2⤊ 0⤋