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COT EXAM QUESTIONS A ND
ANSWERS WITH COMPLET E
SOLUTION
Question : Visible light lies between what wavelengths
(in nanometers)?
Correct answer: Approximately 400-800 nanometers
Question : The wavelength of light makes a difference in
how the eye perceives it. Which characteristics of visible light is determined by its wavelength?
Correct answer: Color
Question : Which color has the longest wavelength? The
shortest?Correct answer: The longest: Red 650 nm-750 nm The
shortest: Blue 446 nm-500 nm
Question : Polarized lenses block all light rays except
those the do what?
Correct answer: Vibrate in the same direction
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Question : What common in-office test uses glasses with
polarized lenses?
Correct answer: Stereopsis (Titmus fly)
Question : Because of refraction a prism bends light rays
toward the base or the apex of the prism. In what units is the power of the prism measured?
Correct answer: Toward the base
Question : The power of a prism to bend light depends on
the size of the angle at the apex of the prism. In what units is the prism measured?
Correct answer: Prism diopters
Question : What does the formula P=C/D represent?
Correct answer: This formula explains the relationship
between the power of prism and ability to bend light. P is prism diopters, C is the displacement of the object in
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centimeters, and D is the distance between the prism and the virtual image in meters
Question : Two prisms places base -to-base form the basis
of what type of lens?
Correct answer: Convex (plus)
Question : Convex (plus) lenses do what to light rays?
Correct answer: Converge them
Question : Two prisms places the apex-to-apex form the
basis of what type of lens?
Correct answer: Concave (minus)
Question : Concave (minus) lenses do what to light rays?
Correct answer: Diverge them
Question : Fresnel prisms are usually applied to the front
surface or the back of a patient's eyeglasses?
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Correct answer: Back surface
Question : What is Pretice's rule?
Correct answer: Its formula to calculate induced prismatic
effect caused by spectacle lenses whose optical centers have been decentered so they are not in line with a
patients visual axis (pupil center). The formula is:
Induced prism (in prism diopters)=lens power (in diopters) X Optical center displacement (in cm)
Question : Find the total amount of prism induced in the
following situations: Glasses RX OD +12.00 sph OS
+10.00 sph - Both optical centers are displaced 5 mm temporally (decentered out)
Correct answer: OD has 6 prism diopters of Base Out /
OS has 5 prism diopters of Base Out / The total is 11 prism diopters of Base Out
Question : Name the variable focusing power of the eye
provided by the flexibility of the crystalline lens.