nao volume 2 questions and answers with verified s
why did the fda ban cellulose nitrate as a frame m
when were lenses first set in frames
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NAO VOLUME 2 QUESTIONS AND ANSWERS
WITH VERIFIED SOLUTIONS 100% CORRECT |
LATEST UPDATE 2025
ED - ANSWER Effective diameter. Twice the longest radius. Used to determine
the smallest lens blank that needs to be cut.
B - ANSWER The vertical box dimension or the vertical distance between two
horizontal tangents to the vertical extremities of the lens shape.
DBL - ANSWER Distance between lenses
DBC - ANSWER Distance between centers. See GC. Frame PD
GC - ANSWER The geometric center of the box, eyewire, or lens shape
OC - ANSWER Optical center. Point of not prism
Why did the FDA ban cellulose nitrate as a frame material? - ANSWER It was
too flammable to be considered safe
When were lenses first set in frames? - ANSWER Late in the 13th century
Who were the first spectacle makers? - ANSWER Goldsmiths
, Which of the following frame materials was not used until the 20th century? -
ANSWER Stainless steal
Why is plastic a popular material for spectacle frames? - ANSWER It can easily
be molded and shaped.
What special care is required for nylon frames? - ANSWER Periodic soaking in
water overnight
What plastic frame material is the only one that can be either pantographed or
injection molded? - ANSWER Cellulose acetate
Which of the following plastics will shrink if over-heated? - ANSWER Polymide
Because this material is black in its original form this plastic must apply color
through the use of baked-on enameling. - ANSWER Carbon fiber
What materials are adjustments the most difficult to achieve due to its tendency
to relax? - ANSWER Kevlar
Which of the following materials recommends "cold snap" lens insertion? -
ANSWER Polymide
Because of its tendency to dry out, the manufacturers of this frame material
recommend that the wearer periodically soak their frames in water over night. -
ANSWER Nylon
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