ABO NOCE Basic Opticianry Ophthalmic Optics 2 — Questions and Answers
Question 1: What is the vergence of light rays that are parallel (coming from optical infinity)?
- Positive vergence
- Zero vergence (Correct answer)
- Negative vergence
- Maximum vergence
Correct answer: Zero vergence
Parallel rays from optical infinity have zero vergence because they are neither converging nor diverging.
Question 2: A lens with a power of -3.00 D will cause light rays to:
- Converge to a focal point 33 cm behind the lens
- Diverge as if from a point 33 cm in front of the lens (Correct answer)
- Converge to a focal point 33 cm in front of the lens
- Have no effect on vergence
Correct answer: Diverge as if from a point 33 cm in front of the lens
A minus (concave) lens diverges light, with its virtual focal point located at 1/3 m = 33 cm in front of the lens.
Question 3: Which law states that the angle of incidence equals the angle of reflection?
- Snell's Law
- Prentice's Rule
- Law of Reflection (Correct answer)
- Fermat's Principle
Correct answer: Law of Reflection
The Law of Reflection states that when light hits a surface, the angle of incidence equals the angle of reflection measured from the normal.
Question 4: The index of refraction of a material is defined as the ratio of:
- The speed of light in a vacuum to the speed of light in the material (Correct answer)
- The speed of light in the material to the speed of light in a vacuum
- The wavelength in the material to the wavelength in air
- The density of the material to the density of air
Correct answer: The speed of light in a vacuum to the speed of light in the material
Index of refraction (n) = speed of light in vacuum (c) divided by speed of light in the medium (v), so n = c/v.
Question 5: What is the primary optical difference between a plano-convex and a biconvex lens of equal power?
- Biconvex has less spherical aberration (Correct answer)
- Plano-convex always has higher Abbe value
- Biconvex produces less chromatic aberration
- Plano-convex is always thinner at the center
Correct answer: Biconvex has less spherical aberration
A biconvex lens distributes refraction more equally across two surfaces, reducing spherical aberration compared to a plano-convex design.
Question 6: When light travels from a medium of lower index to a medium of higher index, it bends:
- Away from the normal
- Toward the normal (Correct answer)
- Parallel to the surface
- At the critical angle
Correct answer: Toward the normal
Light bends toward the normal when entering a denser (higher index) medium, as described by Snell's Law.
Question 7: A prism with its apex pointing upward will deviate a light ray:
- Toward the apex (upward)
- Toward the base (downward) (Correct answer)
- To the left
- No deviation occurs
Correct answer: Toward the base (downward)
Light is always deviated toward the base of a prism, so an apex-up prism deflects rays downward.
ABO NOCE Basic Opticianry Ophthalmic Optics 2
What is the vergence of light rays that are parallel (coming from optical infinity)?