Practice Test GeeksNOCE - National Opticianry Competency Examination Practice Test
← All NOCE Flashcard Decks

Ophthalmic Optics and Lenses Flashcards

7 cards from real NOCE 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 and Lenses flashcards as text

  1. A progressive addition lens (PAL) fitting cross is placed at what anatomical landmark?

    Answer: Pupil center

    The fitting cross of a PAL is aligned with the pupil center to ensure the distance optical center is correctly positioned.

  2. What is the refractive index of standard CR-39 plastic lens material?

    Answer: 1.499

    CR-39 (allyl diglycol carbonate) has a refractive index of approximately 1.499.

  3. Slab-off prism is used to correct vertical imbalance caused by:

    Answer: Anisometropia when reading through off-center lenses

    Slab-off (bicentric grinding) compensates for differential vertical prism induced by anisometropic lenses when the eyes depress for near tasks.

  4. A lens with a power of +4.00 D has a focal length of:

    Answer: 25 cm

    Focal length (meters) = 1 / power (D), so 1/4.00 = 0.25 m = 25 cm.

  5. The phenomenon where a lens splits white light into its component colors is called:

    Answer: Chromatic dispersion

    Chromatic dispersion occurs because different wavelengths of light are refracted by different amounts, separating white light into colors.

  6. An antireflective (AR) coating works by:

    Answer: Destructive interference of reflected light waves

    AR coatings use thin film layers where reflected waves are out of phase and cancel each other through destructive interference.

  7. What does the term 'lenticular lens' describe?

    Answer: A high-power lens with a central optical zone and non-optical carrier

    A lenticular lens has the prescription ground only in a central optical zone (bowl), with a non-prescription carrier that reduces thickness and weight in high-power lenses.