Ophthalmic Optics Questions and Answers Flashcards
7 cards from real ABO NOCE Basic Opticianry practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Ophthalmic Optics Questions and Answers flashcards as text
A lens with a power of +2.00 D has a focal length of:
Answer: 50 cm
Focal length (in meters) equals 1 divided by power in diopters; 1/2.00 = 0.50 m = 50 cm.
Chromatic aberration in ophthalmic lenses is caused by:
Answer: Dispersion of light into its spectral components by the lens material
Different wavelengths of light refract at slightly different angles through a lens, causing chromatic aberration due to material dispersion.
The Abbe value (V-number) of a lens material is used to measure its:
Answer: Resistance to chromatic aberration
A higher Abbe value indicates less chromatic aberration; it measures how well a material keeps colors together.
Which type of lens surface eliminates the tangential and sagittal focus errors simultaneously?
Answer: Atoric
Atoric surfaces are designed to correct both tangential and sagittal oblique astigmatic errors simultaneously.
The refractive index of standard CR-39 plastic lens material is approximately:
Answer: 1.50
CR-39 (allyl diglycol carbonate) has a refractive index of approximately 1.499, commonly cited as 1.50.
When light travels from a denser medium into a less dense medium at an angle exceeding the critical angle, what occurs?
Answer: Total internal reflection
Total internal reflection occurs when light hits the interface at or beyond the critical angle, with no light passing through.
The sagittal depth (sag) of a lens surface is defined as:
Answer: The perpendicular distance from the chord to the surface apex
Sag is the depth of the curve — the perpendicular distance from a flat chord across the lens to the curved surface.