AND 100% CORRECT ANSWERS
0-180 Line
- answers-The horizontal line that goes across the lens.
122,000 Miles per second
- answers-Speed of light per second and crown glass
124,000 Miles per second
- answers-Speed of visible light per second in CR - 39.
140,000 Miles per second
- answers-Speed of visible light Per second in water.
186,000 miles per second
- answers-Speed of visible light Per second in air.
A beam of light
- answers-Is composed of the group of pencils originating from all of the points on a light
source.
A measurement
- answers-The measurement across the imaginary "box". The measurement from
vertical tangent to bevel, horizontally.
A pencil of light
- answers-Is a group of rays divergent from a single point on a light source.
ABBE number
- answers-A measurement of the ability of a material to disperse white light into its
component colors.
Aberrations
- answers-Properties of the lens material or lens design that results in distorted or
blurred images.
Absorption
- answers-Occurs when a futon of light enters a material but does not exit again.
,Against the rules astigmatism
- answers-The shorter of the two focal lengths is horizontal and the correcting lens has
the axis of the minus cylinder with and 30° of the 90° Meridian.
Amblyopia
- answers-A condition in which the eye does not have good correctable vision but has
no physical abnormalities.
Ametropia
- answers-A condition in which the eye has a refractive error.
Amplitude
- answers-The distance from the center of the peak or the valley of a wave.
Angle of incidence
- answers-The angle between a ray of light incident on a surface and the normal to the
surface at the point of incidence. (perpendicular line)
Angle of refraction
- answers-The angle between a ray of light after re-fraction into a material and the
normal to the surface.
Angular magnification
- answers-The ratio of the angle subtended by the image to the angle subtended by the
object when projected on the retina.
Anisometropia
- answers-A condition in which one eye differs significantly in refractive power from the
other eye.
Anisometropia
- answers-And unequal refractive condition between a persons two eyes.
Anti reflective lenses
- answers-AR coated lenses have a metallic oxide coating applied to the surface for the
purpose of lessening reflection from the front, and reflections from the back. Helpful for
people who have trouble seeing in dim light, at night time, and with glare.
Aperture
- answers-An opening or hole that admits only a portion of light from a given source or
sources.
Apex
- answers-The junction point at which the two nonparallel surfaces of a prism meet.
, Astigmatic interval
- answers-The distance between the two focal lengths of a toric or astigmatic lens or
system.
Astigmatism
- answers-The presence of two different curves on a single refracting surface on or
within the eye causing light to focus at two lime images instead of a single point.
Axis meridian
- answers-The meridian of least power of the cylinder or spherocylinder lens.
Axis of a cylinder
- answers-An imaginary reference line used to specify cylinder or spherocylinder lens
orientation and corresponding to the median perpendicular to that of maximum cylinder
power.
B measurement
- answers-The measurement up and down from the horizontal tangent to the bevel. A
vertical measurement.
Back focal length
- answers-The distance from the back surface vertex of a lens to the secondary focal
point.
Barrel
- answers-The housing for a screw on a pair of glasses.
Base
- answers-In a prism, the edge of maximum surface separation opposite the apex.
Bevel
- answers-The angled edge of the spectacle lens.
Block
- answers-Attaches to the surface of a lens in order to hold it in place during the
surfacing or edging process.
Blocker
- answers-The device used to place a block on the lens in order to hold the lens in place
during the edging process.
Boxing system
- answers-The lens makes a "box" of a rectangle with the horizontal and vertical
measurements. This box goes to the edges of the lens or lens blank.