Master Elementary and Physiological Optics – Section 1: Basic Optics with 40 high-yield MCQs on light, reflection, refraction, prisms, and lenses. Covers refractive indices of ocular media, Snell’s law, critical angle, Prentice’s rule, and lens power formulas — essential for NEET PG, AIIMS, INI-CET, and Optometry mcq for exam preparation.
Nature of Light & Basic Concepts
1. The speed of light in vacuum is approximately:
A. 2 × 10⁸ m/s
B. 3 × 10⁸ m/s
C. 1.5 × 10⁸ m/s
D. 2.5 × 10⁸ m/s
View Answer
B. 3 × 10⁸ m/s ✅ Exp: Standard constant c = 3 × 10⁸ m/s.
2. The refractive index (n) is defined as:
A. Velocity in medium / velocity in air
B. Velocity in vacuum / velocity in medium
C. Angle of incidence / angle of refraction
D. 1 / wavelength
View Answer
B. Velocity in vacuum / velocity in medium ✅ Exp: n = c / v.
3. Refractive index of cornea is:
A. 1.333
B. 1.376
C. 1.41
D. 1.39
View Answer
B. 1.376 ✅ Exp: Corneal refractive index ~1.376.
4. The refractive index of aqueous humor is:
A. 1.33
B. 1.34
C. 1.37
D. 1.38
View Answer
A. 1.33 ✅ Exp: Aqueous and vitreous ≈ 1.33.
5. The refractive index of crystalline lens is approximately:
A. 1.40
B. 1.33
C. 1.35
D. 1.50
View Answer
A. 1.40 ✅ Exp: Average 1.40 (varies across nucleus/cortex).
Reflection & Refraction
6. Angle of incidence equals angle of reflection according to:
A. Snell’s law
B. Law of reflection
C. Fermat’s principle
D. Huygens’ principle
View Answer
B. Law of reflection ✅ Exp: Classic law of reflection.
7. Snell’s law relates:
A. Wavelengths
B. Sin i / sin r = n₂ / n₁
C. Velocity only
D. Power of lens
View Answer
B. Sin i / sin r = n₂ / n₁ ✅ Exp: Governs refraction at interface.
8. When light travels from denser to rarer medium, it bends:
A. Toward normal
B. Away from normal
C. No deviation
D. Randomly
View Answer
B. Away from normal ✅ Exp: Less dense medium → away.
9. Critical angle occurs when:
A. Angle of incidence = 90°
B. Angle of refraction = 90°
C. Angle of reflection = 0°
D. No refraction
View Answer
B. Angle of refraction = 90° ✅ Exp: Beyond this → total internal reflection.
10. Total internal reflection is the principle of:
A. Spectacles
B. Contact lenses
C. Optical fibers
D. Convex lens
View Answer
C. Optical fibers ✅ Exp: Used in ophthalmoscopes, fiber optics.
11. Prism deviates light:
A. Towards base
B. Towards apex
C. Towards base of prism
D. Towards normal
View Answer
C. Towards base of prism ✅ Exp: Image shift is towards prism apex, light bends towards base.
12. 1 prism diopter (Δ) deviates light ray by:
A. 0.5 cm at 1 m
B. 1 cm at 1 m
C. 1 cm at 2 m
D. 2 cm at 1 m
View Answer
B. 1 cm at 1 m ✅ Exp: 1Δ = 1 cm deviation at 1 m.
13. In ophthalmology, prisms are commonly used for:
A. Refraction
B. Correction of diplopia & strabismus
C. Astigmatism
D. Accommodation
View Answer
B. Correction of diplopia & strabismus ✅ Exp: Prism glasses for squint/diplopia.
14. Prentice’s rule relates prism power to:
A. Lens thickness
B. Decentration & lens power
C. Focal length only
D. Index of refraction
View Answer
B. Decentration & lens power ✅ Exp: P = cF (c = decentration in cm, F = lens power).
15. Base-out prism is used to correct:
A. Esotropia
B. Exotropia
C. Hypermetropia
D. Myopia
View Answer
A. Esotropia ✅ Exp: Base-out → stimulates convergence, used for esotropia.
16. Power of a lens (in diopters) is:
A. Focal length in cm
B. 100 / focal length (cm)
C. 1 / focal length (m)
D. Focal length in mm
View Answer
C. 1 / focal length (m) ✅ Exp: D = 1 / f (meters).
17. A convex lens is also called:
A. Diverging lens
B. Converging lens
C. Cylindrical lens
D. Plano lens
View Answer
B. Converging lens ✅ Exp: Convex converges light.
18. A concave lens is:
A. Converging lens
B. Diverging lens
C. Neutral lens
D. Prism lens
View Answer
B. Diverging lens ✅ Exp: Concave lens diverges rays.
19. Focal length of +5 D lens is:
A. 50 cm
B. 20 cm
C. 25 cm
D. 5 cm
View Answer
B. 20 cm ✅ Exp: f = 1/5 = 0.2 m = 20 cm.
20. A +2 D lens has focal length of:
A. 2 cm
B. 50 cm
C. 25 cm
D. 1 m
View Answer
B. 50 cm ✅ Exp: f = 1/2 = 0.5 m = 50 cm.
Spherical & Cylindrical Lenses
21. A spherical lens has:
A. Same power in all meridians
B. Different power in each meridian
C. No refractive power
D. Only cylindrical correction
View Answer
A. Same power in all meridians ✅ Exp: Equal curvature in all meridians.
22. A cylindrical lens has:
A. Same power all around
B. Power only in one meridian
C. No refractive effect
D. Prism effect only
View Answer
B. Power only in one meridian ✅ Exp: Corrects astigmatism.
23. Axis of cylindrical lens indicates:
A. Meridian of maximum power
B. Meridian of no power
C. Mean refractive power
D. Optical center
View Answer
B. Meridian of no power ✅ Exp: Cylinder axis = no power.
24. Spherocylindrical lens corrects:
A. Myopia
B. Astigmatism
C. Presbyopia
D. Hypermetropia only
View Answer
B. Astigmatism ✅ Exp: Combination lens corrects astigmatism + spherical error.
25. Cross-cylinder is used in:
A. Retinoscopy
B. Jackson cross cylinder test
C. Keratometry
D. Perimetry
View Answer
B. Jackson cross cylinder test ✅ Exp: JCC used to refine astigmatic axis/power.
Optical Formulas
26. Lensmaker’s formula:
A. P = (n–1)(1/R₁ – 1/R₂)
B. P = n × R
C. P = 1/f only
D. P = (n+1)/R
View Answer
A. P = (n–1)(1/R₁ – 1/R₂) ✅ Exp: Relates refractive index and curvature radii.
27. Vergence (L) is defined as:
A. Distance of object
B. Reciprocal of distance in meters (with sign)
C. Angle of refraction
D. None
View Answer
B. Reciprocal of distance in meters (with sign) ✅ Exp: L = n / l (l = object distance).
28. Equivalent power of two lenses in contact:
A. P = P₁ + P₂
B. P = P₁ × P₂
C. P = (P₁ + P₂)/2
D. P = P₁ – P₂
View Answer
A. P = P₁ + P₂ ✅ Exp: Additive when in contact.
29. Reduced eye model has total refractive power of:
A. 40 D
B. 60 D
C. 80 D
D. 100 D
View Answer
B. 60 D ✅ Exp: Standard schematic eye ~60 D.
30. Principal refractive surface of eye is:
A. Lens
B. Cornea
C. Aqueous
D. Vitreous
View Answer
B. Cornea ✅ Exp: Cornea provides ~43 D of 60 D.
31. An emmetropic eye focuses parallel rays:
A. In front of retina
B. On retina
C. Behind retina
D. No focus
View Answer
B. On retina ✅ Exp: Normal eye focuses exactly on retina.
32. Myopia is corrected by:
A. Convex lens
B. Concave lens
C. Cylindrical lens
D. Prism
View Answer
B. Concave lens ✅ Exp: Diverging lens brings focus back to retina.
33. Hypermetropia is corrected by:
A. Concave lens
B. Convex lens
C. Cylindrical lens
D. Prism
View Answer
B. Convex lens ✅ Exp: Converging lens corrects.
34. Astigmatism correction requires:
A. Prism
B. Cylindrical lens
C. Spherical lens
D. Contact lens only
View Answer
B. Cylindrical lens ✅ Exp: Cylinders correct unequal meridians.
35. Presbyopia is corrected by:
A. Concave lens
B. Convex lens (add power for near)
C. Cylinder lens
D. Prism
View Answer
B. Convex lens (add power for near) ✅ Exp: Reading glasses are convex (plus) lenses.
36. Aphakia correction by spectacles requires:
A. +5 D lens
B. +10 D lens
C. +12 D lens
D. +20 D lens
View Answer
C. +12 D lens ✅ Exp: Aphakic correction ~+10–12 D.
37. High myopia is defined as:
A. >3 D
B. >5 D
C. >6 D
D. >8 D
View Answer
C. >6 D ✅ Exp: ≥ –6.0 D considered high myopia.
38. Rule of thumb: 1 mm change in axial length = refractive error of:
A. 1 D
B. 2.5–3 D
C. 0.5 D
D. 4 D
View Answer
B. 2.5–3 D ✅ Exp: 1 mm = ~3 D refractive shift.
39. Rule of thumb: 1 D change in corneal curvature corresponds to:
A. 0.5 D refractive change
B. 0.7 D refractive change
C. 1 D refractive change
D. 2 D refractive change
View Answer
C. 1 D refractive change ✅ Exp: Keratometry directly reflects corneal power.
40. The most important cause of refractive power in eye is:
A. Lens
B. Cornea
C. Vitreous
D. Aqueous
View Answer
B. Cornea ✅ Exp: Cornea is the strongest refractive surface.
