ABO Optics & Lens Design 1 — Questions and Answers
Question 1: What is the vergence formula used to find image vergence after a lens?
- L' = L + F (Correct answer)
- L' = L - F
- L' = F - L
- L' = L × F
Correct answer: L' = L + F
The vergence formula states that image vergence equals object vergence plus lens power.
Question 2: A lens with a power of +5.00 D has a focal length of:
- 50 cm
- 20 cm (Correct answer)
- 10 cm
- 5 cm
Correct answer: 20 cm
Focal length = 1/power, so 1/5 = 0.20 m = 20 cm.
Question 3: Which lens type is used to correct myopia?
- Convex (plus)
- Plano
- Concave (minus) (Correct answer)
- Prism
Correct answer: Concave (minus)
Concave minus lenses diverge light to shift the focal point back onto the retina in myopic eyes.
Question 4: The approximate index of refraction of standard crown glass is:
- 1.40
- 1.52 (Correct answer)
- 1.60
- 1.74
Correct answer: 1.52
Standard crown glass has a refractive index of approximately 1.523, making it the traditional ophthalmic lens baseline.
Question 5: A higher Abbe value (V-number) in a lens material indicates:
- Greater impact resistance
- Better UV protection
- Less chromatic aberration (Correct answer)
- Higher refractive index
Correct answer: Less chromatic aberration
A higher Abbe value means less dispersion of light into its component colors, resulting in less chromatic aberration.
Question 6: The base curve of a spectacle lens primarily affects:
- UV transmission
- Lens weight alone
- Cosmetic appearance and peripheral optics (Correct answer)
- Scratch resistance
Correct answer: Cosmetic appearance and peripheral optics
The base curve selection affects both the cosmetic profile and peripheral optical performance of spectacle lenses.
ABO Optics & Lens Design 1
What is the vergence formula used to find image vergence after a lens?