ABO NOCE Basic Opticianry Ophthalmic Optics and Principles Questions and Answers 2 — Questions and Answers
Question 1: A lens has a power of +2.50 D. What is its focal length in meters?
- 0.25 m
- 0.40 m (Correct answer)
- 2.50 m
- 0.50 m
Correct answer: 0.40 m
Focal length = 1 / Power, so 1 / 2.50 = 0.40 meters.
Question 2: Which type of aberration causes light rays at different distances from the optical axis to focus at different points, resulting in a blurred image?
- Chromatic aberration
- Coma
- Spherical aberration (Correct answer)
- Distortion
Correct answer: Spherical aberration
Spherical aberration occurs when peripheral rays focus at a different point than paraxial rays due to the curvature of the lens.
Question 3: What is the index of refraction of a material if light travels through it at 2.0 × 10⁸ m/s (speed of light in air = 3.0 × 10⁸ m/s)?
- 0.67
- 1.50 (Correct answer)
- 2.00
- 1.33
Correct answer: 1.50
Index of refraction n = speed of light in air / speed of light in medium = 3.0/2.0 = 1.50.
Question 4: A prism displaces an image toward which direction relative to its base?
- Toward the base
- Toward the apex (Correct answer)
- Perpendicular to the base
- No displacement occurs
Correct answer: Toward the apex
Light is refracted toward the base of a prism, so the image appears displaced toward the apex.
Question 5: When light passes from a denser medium to a less dense medium at an angle exceeding the critical angle, what occurs?
- Refraction
- Total internal reflection (Correct answer)
- Dispersion
- Diffraction
Correct answer: Total internal reflection
Total internal reflection occurs when light exceeds the critical angle at the boundary between a denser and less dense medium.
Question 6: What is the add power for a patient whose distance Rx is +1.00 D and near Rx is +3.00 D?
- +4.00 D
- +2.00 D (Correct answer)
- +1.00 D
- -2.00 D
Correct answer: +2.00 D
Add power = near Rx minus distance Rx = +3.00 − (+1.00) = +2.00 D.
Question 7: A cylinder lens with axis at 180° corrects which meridian of the eye?
- 180° meridian
- 90° meridian (Correct answer)
- Both meridians equally
- The oblique meridians only
Correct answer: 90° meridian
A cylinder with axis at 180° has no power in the 180° meridian and full power in the 90° meridian, correcting the 90° meridian.
ABO NOCE Basic Opticianry Ophthalmic Optics and Principles Questions and Answers 2
A lens has a power of +2.50 D.
What is its focal length in meters?