NAO VOLUME IV EXAM QUESTIONS AND
ANSWERS
The amount of reflection of each surface of CR-39 plastic lenses is approximately: - ANSWER-4%
The absorption of light in lenses is classified by two variables. What are they? - ANSWER-Tint and
lens transmission
The denser the tint in a lens, the _____:...
Although this may be the most popular color for sunlenses, it is not recommended for patients with
emerging cataracts: - ANSWER✔✔-gray
_____ added to any color increases contrast: - ANSWER✔✔-yellow
_____ is better than _____ for improving contrast: - ANSWER✔✔-green
Glare is of more concern to which wearer? - ANSWER✔✔-cataract patient
_____ are generally inorganic materials (metals or minerals) that are vacuum deposited to add color on
glass lenses to give a uniform density of color on the lenses: - ANSWER✔✔-vacuum color coatings
Which company introduced CR-39 plastic lenses? - ANSWER✔✔-PPG Industries
What is the index of refraction of polycarbonate? - ANSWER✔✔-1.59
The quality of today's polycarbonate lenses has been improved due to the demand of what product? -
ANSWER✔✔-compact discs
Birefringence is also referred to as _____ and can result in distortion reducing the visual performance to
the wearer? - ANSWER✔✔-double refraction
What is the index of refraction of trivex? - ANSWER✔✔-1.53
Features and benefits of trivex include_____: - ANSWER✔✔-superior optics, impact resistance, ultra-
light weight (all of the above)
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