Quiz 4 Flashcards
CR-39 is: -Tintable and scratch proof -Tintable and somewhat scratchable -Tintable and very thin -Somewhat scratchable and very thin
Tintable and somewhat scratchable
Polycarbonate is: -Low babe value -Used as a safety material -Light weight -All of these
All of these
High Index lenses are rarely used for: -Rimless glasses -Sunglasses -Safety glasses -Reading glasses
Safety Glasses
What is the approximate speed of light in air?
186,000 miles per second
What happens to light as it passes from air into a refractive material such as glass?
It slows down.
Index of refraction is a ratio of the speed of light in the material to the speed of light in:
Air.
Put the following lens materials in order of weight from heaviest to lightest: Glass High Index CR39 Polycarbonate
Glass, CR-39, High Index, Polycarbonate
Trifocals have how many focal points?
3
High Index is the most impact-resistant lens material True or False
False
Glass is the most scratch-resistant lens material. True or False
True
A stocked lens already prepared with a power is known as a ___________ lens.
Finished
To surface a prescription a/an ____________ lens should be selected.
Semi-Finished
The following is a disadvantage of glass: -High abbé value -Poor impact resistance -Light weight -Scratch Resistant
Poor Impact Resistance
The blank size of a lens is measured in ….
Millimeters.
The true curve of a lens is determined form the sag value. True or False
True
Which of the following images presents a semi-finished lens?
Which of the following images presents a finished lens?
A bifocal lens has:
.2 focal points
Put the following lenses in order of Index of Refraction; lowest to highest. High Index, Crown Glass, CR-39, Polycarbonate, Trivex
CR-39, Crown Glass, Trivex, Polycarbonate, High-Index
The following are advantages of glass: -Low abbé and resistant to scratching -Heavy and superior optics -Very scratchable and heavy -Superior optics and low chromatic aberration
Superior optics and low chromatic aberation
