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NAO Volume II – Questions & Expert Verified Answers
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NAO Volume II – Questions & Expert Verified Answers
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NAO Volume II – Questions & Expert Verified AnswersWhat is the central layer of an iZon lens made of?
A. A Hartman-Shack lens set array
B. 1.60 index plastic
C. Zernike Polynomials
D. A liquid polymer Right Ans - D. A liquid polymer
Asborption Right Ans - When a ray of light enters a lens some of the light
will not completely travel through the lenses
Deviation (angle of) Right Ans - The angle a ray of light is changed from its
original path
Diffuse Reflection Right Ans - A reflection from a rough surface-the
reflection does not produce a clear image
Incidence Right Ans - The angle which a ray of light makes with the surface
of a refracting medium
Reflection Right Ans - The return of light waves from a surface. The
production of an image
Refraction Right Ans - The bending of light when going from one medium
into another.
(Angle of)Refraction Right Ans - The angle created when a ray of light
passes from one medium into another
Specular Reflection Right Ans - The forming of a clear image when light
strikes a surface
When is the pencil red? Right Ans - It reflects the red rays back toward the
eye and absorbs all other rays of visible light
Why is the blacktop black? Right Ans - It does not reflect any rays back
toward your eye; rather, it absorbs them all
,If a light beam passes through a green sunglass lenses, why will the light
exiting light be green? Right Ans - The green rays are refracted through the
lens and all other color rays are absorbed by the pigments in the lens material.
What does critical angle mean? Right Ans - A light of ray leaving a denser
material for a rarer material that is at an angle to the normal that results in it
traveling parallel to the surface of the material. If the angle of incidence is
greater than the critical than the critical angle the ray will reflect inside the
material and will not exit into the rarer material.
Focal Power Formula Right Ans - D=1/f
Power in Oblique meridians Right Ans - TP=sphere power +cylinder power
x sin(2) squared
Snell's Law Right Ans - N1 sin I = N(2) sin r
Law of reflection Right Ans - angle i = angle r
Prentice Rule Right Ans - Prism = (h+D)/10
Nominal power Right Ans - D(e) = D(1)+D(2)
Frame PD Right Ans - FPD = A +DBL
Binocular decentration Right Ans - Dec= (FPD-PPD)/2
Index of refraction Right Ans - speed of light in air/speed of light in
medium
Minimum black size Right Ans - MBS= ED + (2xDec)
What is the difference between a high index lens and an aspheric lens?
Right Ans - High index refers to the material of the lens; aspheric refers to the
surface design of the lens
What are the three things that can happen to a ray of light when it passes
through a lens? Right Ans - Reflection, Absorption, Refraction
,What role does the FDA (food & drug administration) play in the ophthalmic
industry? Right Ans - They are responsible for the lens safety aspect of the
industry. Impact resistant is their main focus.
According to the Systems text, eyewear can be divided in to what three
categories? Right Ans - Dress eyewear: Designed for everyday use
Safety eyewear: Designed to meet the standard of impact resistance since it
will be worn in situations that could be potentially hazardous to the eyes
Sports eyewear: Designed to protect the eyes or enhance the vision in specific
sports situations.
What is transposition? Right Ans - The changing of a prescription from plus
cylinder to minus cylinder or the other way around (there is no effect on the
powers of the prescription).
What type of image is formed by a minus lens? Right Ans - Virtual
A plus lens does what to light rays that pass through it? Right Ans - Makes
them converge
What does the term critical angle of a material mean? Right Ans - The ray
of light is striking the surface of an angle so that the ray is refracted along the
surface of the lens.
A minus lens with the optical center moved up creates? Right Ans - Base
down prism
What three things does base up prism cause? Right Ans - 1. Bends light
towards the base
2. Bends light rays away from the apex
3. Projects an image of the object downwards
What are the wavelengths visible light range? Right Ans - 400-720
nanometers
What are the wavelengths are that most pleasing to the eye? Right Ans -
Blue-Green
, The breakdown of light into its component colors is known as? Right Ans -
Dispersion
The point on a lens which a ray of light will pass through without being
deviated is called? Right Ans - Optical center
The lower the Abbe value, the .............. Right Ans - More the chromatic
aberrations
Which lens has the characteristic of magnification? Right Ans - Plus
spherical
Which lens has the characteristic of thin center/thick edge? Right Ans -
Minus spherical
Which lens has the characteristic of diverging light rays? Right Ans - Minus
spherical
Which lens has the characteristic of with motion? Right Ans - Minus
spherical
The lens design in which the front base curve gradually flattens is called?
Right Ans - aspherical
Rounded frames are recommended for high minus lenses and squared frames
are recommended for high plus lenses.
True or False Right Ans - False
The lower the frame bridge, the greater the effect of.........? Right Ans -
Shortening the nose
Which type of temple curves around the ear following the crotch of the ear
where war and head meet, extending to the level of the earlobe? Right Ans -
Riding bow
Which frame material can be made thin and lightweight, with frame colors
that are primarily opaque? Some problems may be encountered with
breakage in cold weather/ Right Ans - Carbon fiber
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