ABO NOCE Basic Opticianry Ophthalmic Optics 5 — Questions and Answers
Question 1: According to Prentice's Rule, a lens of +2.00 D with the optical center decentered 5 mm will produce how many prism diopters?
- 0.5 Δ
- 1.0 Δ (Correct answer)
- 2.5 Δ
- 10.0 Δ
Correct answer: 1.0 Δ
Prentice's Rule: Prism (Δ) = Power (D) × Decentration (cm) = 2.00 × 0.5 cm = 1.0 Δ.
Question 2: An object is placed 33 cm in front of a +4.00 D lens. Where does the image form?
- 33 cm behind the lens
- 50 cm behind the lens
- 100 cm behind the lens (Correct answer)
- No real image forms
Correct answer: 100 cm behind the lens
Incoming vergence U = -1/0.33 = -3.00 D; V = P + U = 4.00 + (-3.00) = +1.00 D; image distance = 1/1.00 = 1.0 m = 100 cm behind the lens.
Question 3: What is the dioptric power of a surface with a radius of curvature of 0.10 m separating air (n=1.0) from glass (n=1.5)?
- +1.50 D
- +5.00 D (Correct answer)
- +10.00 D
- +0.50 D
Correct answer: +5.00 D
Surface power = (n2 - n1) / r = (1.5 - 1.0) / 0.10 = 0.5 / 0.10 = +5.00 D.
Question 4: When transposing +2.00 -3.00 x 045 to plus-cylinder form, the result is:
- -1.00 +3.00 x 135 (Correct answer)
- -1.00 +3.00 x 045
- +2.00 +3.00 x 135
- -3.00 +2.00 x 045
Correct answer: -1.00 +3.00 x 135
To transpose: new sphere = algebraic sum (+2.00 - 3.00 = -1.00); change cylinder sign (+3.00); rotate axis 90° (045 + 90 = 135°), giving -1.00 +3.00 x 135.
Question 5: What property of light determines its color as perceived by the human eye?
- Amplitude (intensity)
- Wavelength (Correct answer)
- Speed
- Polarization state
Correct answer: Wavelength
The perceived color of light is determined by its wavelength, with visible light ranging from approximately 380 nm (violet) to 780 nm (red).
Question 6: The secondary focal point of a converging lens is located:
- On the same side as the incoming light
- On the opposite side from the incoming light (Correct answer)
- At the lens itself
- At infinity for all plus lenses
Correct answer: On the opposite side from the incoming light
The secondary (rear) focal point of a converging (plus) lens is where parallel rays from the front converge, located on the opposite side from the incoming light.
Question 7: Which of the following best describes a toric lens surface?
- A surface with the same radius of curvature in all meridians
- A surface with two different principal radii of curvature at 90° to each other (Correct answer)
- A surface that is perfectly flat
- A surface with continuously varying power across the entire lens
Correct answer: A surface with two different principal radii of curvature at 90° to each other
A toric surface has two principal meridians of different curvature oriented 90° apart, which is what creates the cylinder (astigmatic) correction.
ABO NOCE Basic Opticianry Ophthalmic Optics 5
According to Prentice's Rule, a lens of +2.00 D with the optical center decentered 5 mm will produce how many prism diopters?