Explore 40 important Physical Optics MCQ on Basic Optics, Lenses & Ophthalmic Instruments with answers and explanations. Perfect for Optometry students and exam preparation. Learn about light, refraction, Snell’s law, lens power, aberrations, and optical principles only on MCQ Zone. View More Ophthalmology and Optometry MCQ.
Q1. Light travels in straight lines called:
A. Rays
B. Waves
C. Particles
D. Diffusions
View Answer
A. Rays ✅ Exp: Optical rays represent the path of light propagation.
Q2. Speed of light in air is approximately:
A. 1.5 × 10⁸ m/s
B. 3 × 10⁸ m/s
C. 2 × 10⁸ m/s
D. 1 × 10⁸ m/s
View Answer
B. 3 × 10⁸ m/s ✅ Exp: The speed of light in air/vacuum is about 3 × 10⁸ m/s.
Q3. Refractive index (n) is defined as:
A. Speed in air ÷ speed in medium
B. Speed in medium ÷ speed in air
C. Speed² ratio
D. Wavelength ratio
View Answer
A. Speed in air ÷ speed in medium ✅ Exp: ; higher refractive index → slower light speed.
Q4. When light enters a denser medium:
A. Bends away from the normal
B. Bends toward the normal
C. No bending
D. Total reflection
View Answer
B. Bends toward the normal ✅ Exp: Light slows and bends toward the normal in a denser medium.
Q5. Snell’s law states that:
A. sin i / sin r = constant
B. i + r = 90°
C. sin r / sin i = 1
D. tan i = tan r
View Answer
A. sin i / sin r = constant ✅
Q6. The refractive index of the cornea is approximately:
A. 1.33
B. 1.376
C. 1.40
D. 1.50
View Answer
B. 1.376 ✅ Exp: Corneal refractive index = 1.376.
Q7. The refractive index of aqueous and vitreous humor is approximately:
A. 1.40
B. 1.336
C. 1.33
D. 1.30
View Answer
B. 1.336 ✅ Exp: Both humors have similar refractive indices ≈ 1.336.
Q8. The critical angle occurs when:
A. Light enters rarer to denser
B. Refraction = 90°
C. Total reflection begins
D. Reflection = refraction
View Answer
B. Refraction = 90° ✅ Exp: Critical angle → angle of incidence producing 90° refraction.
Physical Optics MCQ
Q9. Total internal reflection occurs when light:
A. Travels from denser to rarer medium
B. Rarer to denser
C. Parallel to normal
D. Hits at 90°
View Answer
A. Travels from denser to rarer medium ✅ Exp: Occurs only when incidence > critical angle.
Q10. Ophthalmoscopes work on the principle of:
A. Total internal reflection
B. Refraction
C. Diffraction
D. Polarization
View Answer
A. Total internal reflection ✅ Exp: Mirrors/prisms use TIR to direct light into and out of the eye.
Physical Optics Mcq
Q11. Vergence (V) of light is given by:
A. n / distance (in m)
B. 1 / distance
C. n × distance
D. Speed / n
View Answer
A. n / distance (in m) ✅ Exp: V = n/l; unit = Diopter (D).
Q12. Parallel rays have a vergence of:
A. 0 D
B. +1 D
C. –1 D
D. Infinite D
View Answer
A. 0 D ✅ Exp: Parallel rays have zero vergence (no curvature).
Q13. Divergent rays have:
A. Positive vergence
B. Negative vergence
C. Zero
D. Variable
View Answer
B. Negative vergence ✅ Exp: Diverging rays are assigned negative vergence.
Q14. The power of a lens (P) is:
A. 1/f (in meters)
B. f × n
C. f / 1
D. 1/f²
View Answer
A. 1/f (in meters) ✅ Exp: Lens power = reciprocal of focal length (in meters).
Q15. A +5 D lens has focal length:
A. 5 cm
B. 20 cm
C. 50 cm
D. 25 cm
View Answer
B. 20 cm ✅
Q16. A –2 D lens has a focal length of:
A. +50 cm
B. –50 cm
C. 25 cm
D. –25 cm
View Answer
B. –50 cm ✅ Exp: Negative → virtual focus on the same side as object.
Q17. If rays converge 1 m behind a lens, its power is:
A. +1 D
B. –1 D
C. +0.5 D
D. –2 D
View Answer
A. +1 D ✅
Q18. The unit of refractive power is:
A. Meter
B. Diopter
C. Candela
D. Lux
View Answer
B. Diopter ✅ Exp: 1 D = 1/m (reciprocal meter).
Q19. When two thin lenses of +2 D and +3 D touch, total power =
A. +6 D
B. +5 D
C. +4 D
D. –1 D
View Answer
B. +5 D ✅ Exp: Combined power = F₁ + F₂ = +5 D.
Q20. If the lenses (+2 D and +3 D) are 10 cm apart, combined power ≈
A. +5 D
B. +4.7 D
C. +6 D
D. +3 D
View Answer
B. +4.7 D ✅ Exp: ; d = 0.1 m.
Q21. A real image forms when rays:
A. Appear to diverge
B. Actually converge
C. Do not meet
D. Are reflected
View Answer
B. Actually converge ✅ Exp: Real images form by actual intersection of rays.
Q22. A virtual image forms when rays:
A. Converge
B. Appear to diverge
C. Reflect
D. Pass through the center
View Answer
B. Appear to diverge ✅ Exp: Virtual image appears behind lens where rays seem to meet.
Q23. A convex lens acts as a magnifier when:
A. Object between F and 2F
B. Object between lens and F
C. Object at infinity
D. Object beyond 2F
View Answer
B. Object between lens and F ✅ Exp: Object within focal point → virtual, erect, magnified image.
Q24. A concave lens always forms:
A. Real inverted image
B. Virtual erect diminished image
C. Real magnified
D. Inverted magnified
View Answer
B. Virtual erect diminished image ✅ Exp: Concave lens diverges rays, forming small virtual image.
Q25. Power of a plane surface is:
A. +1 D
B. 0 D
C. –1 D
D. +0.5 D
View Answer
B. 0 D ✅ Exp: Plane surface has infinite radius → zero refractive power.
Q26. Lens maker’s formula:
A. 1/f = (n – 1)(1/R₁ – 1/R₂)
B. f = n – 1
C. R₁ × R₂ = f²
D. None
View Answer
A. 1/f = (n – 1)(1/R₁ – 1/R₂) ✅ Exp: Determines focal length from surface curvatures and refractive index.
Q27. A lens in water has power that is:
A. Increased
B. Decreased
C. Same
D. Doubled
View Answer
B. Decreased ✅ Exp: Reduced refractive difference between lens and medium decreases power.
Q28. Lens maker’s formula is used to find:
A. Power of a lens
B. Thickness
C. Dispersion
D. Prism power
View Answer
A. Power of a lens ✅
Q29. A lens with equal curvature on both sides is:
A. Biconvex
B. Plano-convex
C. Meniscus
D. Plano-concave
View Answer
A. Biconvex ✅ Exp: Equal radii → symmetric biconvex lens.
Q30. Total optical power of the human eye is:
A. +30 D
B. +60 D
C. +40 D
D. +70 D
View Answer
B. +60 D ✅ Exp: Cornea ≈ 43 D, lens ≈ 17 D → total ≈ +60 D.
Q31. Chromatic aberration is due to:
A. Different refraction for different wavelengths
B. Spherical curvature
C. Scattering
D. Reflection
View Answer
A. Different refraction for different wavelengths ✅ Exp: Blue light refracts more than red light → dispersion.
Q32. Longitudinal chromatic aberration corrected by:
A. Achromatic doublets
B. Concave mirrors
C. Plano-convex lenses
D. Large pupils
View Answer
A. Achromatic doublets ✅ Exp: Combining flint & crown glass lenses cancels dispersion.
Q33. Spherical aberration occurs when:
A. Peripheral rays focus at different points
B. Chromatic dispersion
C. Foveal shift
D. Iris displacement
View Answer
A. Peripheral rays focus at different points ✅ Exp: Peripheral rays refract more → multiple foci.
Q34. Coma aberration occurs due to:
A. Off-axis light rays
B. Lens curvature only
C. Chromatic dispersion
D. Reflection errors
View Answer
A. Off-axis light rays ✅ Exp: Produces comet-like blur for off-axis images.
Physical Optics MCQ
Q35. Astigmatism is due to:
A. Unequal curvature in different meridians
B. Different wavelengths
C. Retinal disease
D. Tear film instability
View Answer
A. Unequal curvature in different meridians ✅ Exp: Causes two focal lines instead of a single point focus.
Q36. Distortion aberration produces:
A. Barrel or pincushion effect
B. Color blur
C. Glare
D. Ghost image
View Answer
A. Barrel or pincushion effect ✅ Exp: Unequal magnification across image → distortion.
Q37. The refractive index of crown glass ≈
A. 1.45
B. 1.523
C. 1.60
D. 1.65
View Answer
B. 1.523 ✅ Exp: Common optical glass used for achromatic lenses.
Q38. Flint glass has refractive index:
A. 1.50
B. 1.60–1.70
C. 1.45
D. 1.40
View Answer
B. 1.60–1.70 ✅ Exp: High-dispersion glass used in achromatic combinations.
Q39. Abbe’s number measures:
A. Dispersion
B. Density
C. Reflectivity
D. Refractive power
View Answer
A. Dispersion ✅ Exp: Higher Abbe number → lower chromatic dispersion.
Q40. The main cause of glare in optical systems is:
A. Scattering
B. Diffraction
C. Total reflection
D. Refraction
View Answer
A. Scattering ✅ Exp: Scattered light from imperfections causes glare.
Physical Optics MCQ
