Ray Optics and Optical InstrumentsNEET MCQs with solutions
Ray Optics is one of NEET's highest-weightage Physics chapters. Reflection, refraction, lenses, mirrors, prisms, total internal reflection, optical instruments (microscope, telescope) and power of lens are all tested. Mirror and lens formula numericals, prism dispersion and TIR conditions dominate NEET questions.
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Tap an option to check it. Questions from every NCERT topic in this chapter, from easy to hard.
Q1Mixed Revision
A plane mirror forms an image of a real object. Which combination correctly describes the image?
Not quite — the answer is D.
A plane mirror forms a virtual, erect, laterally inverted image of the same size (m = +1) at equal distance behind the mirror. It can never form a real or diminished image. Option C trap: confusing plane mirror with concave mirror used as magnifier.
Q2Mixed Revision
At minimum deviation through a prism of angle A, which of the following sets of conditions holds simultaneously?
Not quite — the answer is C.
At minimum deviation, the ray traverses the prism symmetrically: angle of incidence equals angle of emergence (i = e) and each internal angle r₁ = r₂ = A/2. Option A is a trap where students correctly recall i = e but write r = A instead of A/2.
Q3Grand Test
A person can see clearly only up to 80 cm. The power of the corrective lens required to see distant objects clearly is
Not quite — the answer is D.
For u = -∞ and v = -0.80 m, P = 1/v - 1/u = -1/0.80 = -1.25 D. A concave lens diverges rays to shift the far point to infinity.
Q4Grand Test
A ray is incident at angle i on one face of a small-angle prism of angle A and emerges normally from the opposite face. If the refractive index of the prism is μ, the approximate angle of incidence is
Not quite — the answer is C.
Since the ray emerges normally, r2 = 0 so r1 = A. Snell's law gives sin i = μ sin A. For small angles, i ≈ μA. Option A inverts the refractive index ratio.
Q5Reflection by Spherical Mirrors
An object is placed on the principal axis of a concave mirror at a distance of 1.5f, where f is the magnitude of the focal length. The image will be formed at
Not quite — the answer is A.
With u = -1.5f and f_mirror = -f: 1/v = -1/f + 1/(1.5f) = -1/(3f), so v = -3f. Negative v confirms a real image in front of the mirror. Common error: using f positive for concave mirror gives v = +3f, a wrong virtual image.
Q6Reflection by Spherical Mirrors
The graph of 1/v versus 1/u for a concave spherical mirror is best described as
Not quite — the answer is C.
From 1/v = 1/f - 1/u, the graph of 1/v vs 1/u is a straight line with slope -1. For a concave mirror, f is negative, so the y-intercept 1/f is negative. Option B fails because the y-intercept is negative, not positive.
Q7Prism & Dispersion
At minimum deviation through a prism of angle A, which set of relations is correct?
Not quite — the answer is A.
The ray path is symmetric at minimum deviation. Hence i = e and r₁ = r₂. Since r₁+r₂ = A, each internal angle equals A/2. Options C and D are wrong because they set one or both surface angles equal to A, which is the prism angle, not the refraction angle.
Q8Prism & Dispersion
At minimum deviation through a prism, which of the following correctly describes the internal ray path?
Not quite — the answer is B.
At minimum deviation r₁ = r₂ = A/2, making the internal ray symmetric. This means the ray inside the prism is parallel to the base. Option A is wrong because refraction occurs at both surfaces. Option C confuses TIR with minimum deviation.
Q9Human Eye
A person can see clearly only between 50 cm and 400 cm from his eyes. To extend the maximum distance of distinct vision to infinity, the type and power of corrective lens required is
Not quite — the answer is B.
Far point is 4 m. For u=-infinity, corrective lens needs v=-4 m. P=1/f=1/(-4)=-0.25 D, so a concave lens of -0.25 D is needed. Option A is wrong as myopia needs a concave not convex lens.
Q10Human Eye
For a normal eye, the cornea has converging power 40 D and the eye lens minimum converging power is 20 D. The distance between the retina and the cornea-eye-lens system is approximately
Not quite — the answer is C.
Total minimum power for distant vision = 40+20 = 60 D. Focal length f = 1/60 m = 0.0167 m = 1.67 cm. For a distant object, image forms at retina, so retina is ~1.67 cm from the lens system.
Q11Optical Instruments
A compound microscope has an objective of focal length 2 cm, eyepiece of focal length 4 cm and tube length 40 cm. Taking D = 25 cm, its approximate magnifying power when the final image is at the near point is
Not quite — the answer is B.
M = (L/f_o)(D/f_e) = (40/2)(25/4) = 20 x 6.25 = 125. Option A is the trap: students use D/f_e = 25/4 = 6.25 without the 1 + term and then multiply (40/2) x 5 = 100, confusing the two conditions.
Q12Optical Instruments
A small astronomical telescope has an objective focal length of 140 cm and an eyepiece focal length of 5 cm. The magnitude of its angular magnifying power in normal adjustment is
Not quite — the answer is A.
In normal adjustment, |M| = f_o/f_e = 140/5 = 28. Option B (14) is the trap from students who halve f_o incorrectly. Option C (35) arises from adding f_e to the numerator: (140+5)/5 = 29, rounded to 35 — a tube-length confusion error.
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Get RankUp on Google PlayQ13Thin Lenses & Lens Formula
An object is placed 20 cm in front of a convex lens of focal length 15 cm. The image distance is
Not quite — the answer is A.
Using 1/v - 1/u = 1/f with u = -20 cm, f = +15 cm: 1/v = 1/15 - 1/20 = 1/60, so v = +60 cm. Option B (30 cm) is the trap from using f - u instead of the full formula.
Q14Thin Lenses & Lens Formula
A convex lens has radii of curvature R1 = +30 cm and R2 = -30 cm. If the refractive index of the lens is 1.5, its focal length is
Not quite — the answer is B.
Lens maker's equation: 1/f = (n-1)(1/R1 - 1/R2) = 0.5(1/30 - 1/(-30)) = 0.5(2/30) = 1/30, so f = +30 cm. Trap: students who forget the negative sign of R2 halve the answer and get 60 cm.
Q15Combination of Thin Lenses
Two thin lenses of focal lengths +10 cm and −30 cm are placed in contact. A real object is placed 20 cm in front of the combination. The image distance from the combination is
Not quite — the answer is A.
1/F = 1/10 − 1/30 = 2/30, so F = +15 cm. Lens formula: 1/v = 1/15 − 1/20 = 1/60, giving v = +60 cm. Trap: students use u = +20 cm instead of −20 cm, getting a wrong sign for v.
Q16Combination of Thin Lenses
A convex lens of focal length 20 cm and a concave lens of focal length 40 cm are placed in contact. The focal length of the combination is
Not quite — the answer is A.
1/F = 1/20 − 1/40 = 1/40, so F = +40 cm. The combination remains converging. Trap: adding focal lengths directly gives 60 cm, which is wrong because reciprocals must be added.
Q17Lens Maker's Formula & Power of Lens
A biconvex glass lens has refractive index 1.5 and radii of curvature 20 cm each. Its power in air is
Not quite — the answer is B.
1/f = (0.5)(1/0.20 + 1/0.20) = 0.5 × 10 = 5 m⁻¹, so P = +5 D. Trap A (+2 D) comes from computing (0.5)(1/0.20) alone, forgetting the second surface contributes equally.
Q18Lens Maker's Formula & Power of Lens
The power of an equiconvex lens is 10 D and the radius of curvature of each surface is 10 cm. The refractive index of the lens material is
Not quite — the answer is D.
1/f = (μ−1)(2/R): 10 = (μ−1)(2/0.10) = 20(μ−1) → μ−1 = 0.5 → μ = 1.5 = 3/2. Trap C (5/3 ≈ 1.67) arises from students computing 2/R first then forgetting to divide by the power correctly.
Q19Total Internal Reflection & Optical Fibres
Light travels from glass (refractive index 1.5) to air. The critical angle for the glass-air interface is approximately
Not quite — the answer is B.
sin C = 1/μ = 1/1.5 = 0.667, giving C ≈ 41.8°. A common trap is inverting incorrectly to sin C = μ = 1.5, which is physically impossible since sin C cannot exceed 1.
Q20Total Internal Reflection & Optical Fibres
For total internal reflection to occur at a boundary between two transparent media, which combination of conditions is necessary?
Not quite — the answer is C.
TIR requires propagation from denser to rarer medium AND i > C. Option D fails because at i = C the refracted ray merely grazes the interface; complete reflection begins only for i > C.
Q21Refraction at Spherical Surfaces
A convex spherical refracting surface separates air (n₁ = 1) from glass (n₂ = 1.5), R = +10 cm. A point object in air is placed 30 cm in front of the surface. The image distance is
Not quite — the answer is C.
n₂/v − n₁/u = (n₂−n₁)/R: 1.5/v + 1/30 = 0.5/10 = 1/20 → 1.5/v = 1/20 − 1/30 = 1/60 → v = +90 cm. Positive v confirms real image on transmission side. Trap: using R = −10 (wrong sign for C on transmission side) gives a negative v, implying virtual image.
Q22Refraction at Spherical Surfaces
For refraction at a spherical surface, the formula is n₂/v − n₁/u = (n₂−n₁)/R. If n₁ = n₂, this formula reduces to
Not quite — the answer is A.
When n₁ = n₂, the RHS = 0. The equation becomes n/v = n/u, giving v = u: the image coincides with the object. Physically, no refractive-index change means no bending occurs and the ray continues undeviated.
Q23Refraction at Plane Surfaces & Refractive Index
A ray of light is incident from air on a glass slab at an angle of incidence 60°. If the angle of refraction is 45°, the refractive index of glass is
Not quite — the answer is A.
By Snell's law: n = sin 60° / sin 45° = (√3/2)/(1/√2) = √6/2 ≈ 1.22. Option B (√3) arises from using sin 45° = 1/2 instead of 1/√2 — the most common trigonometric substitution error in this calculation.
Q24Refraction at Plane Surfaces & Refractive Index
A ray of light travels from air into a medium of refractive index √2 with an angle of incidence 45°. The angle of refraction is
Not quite — the answer is B.
sin r = sin 45°/√2 = (1/√2)/√2 = 1/2, so r = 30°. Option C (45°) is the trap — students assume no bending occurs. Option A (60°) results from inverting the refractive index ratio.
ELITE question · AIR under 50 level
This chapter has 229 ELITE questions for students aiming at the very top. They are only in the app.
Unlock ELITE questions in the appKey Optics Formulas
Quick revision: most questions in this chapter test these facts.
| Concept | Key Formula |
|---|---|
| Mirror formula | 1/v + 1/u = 1/f; magnification m = −v/u |
| Lens formula | 1/v − 1/u = 1/f; magnification m = v/u |
| Power of lens | P = 1/f (in metres); unit: dioptre (D); convex +, concave − |
| Snell's law | n₁ sinθ₁ = n₂ sinθ₂; n = c/v |
| Total internal reflection | sinθ_c = n₂/n₁ (n₁ > n₂); θ > θ_c → TIR; used in optical fibre |
| Prism | δ = (μ−1)A (thin prism); δ_min when i = e, r₁ = r₂ = A/2 |
What the app covers in this chapter
601 questions in total, each with a detailed explanation.
| Mixed Revision | 155 |
| Grand Test | 93 |
| Reflection by Spherical Mirrors | 40 |
| Prism & Dispersion | 40 |
| Human Eye | 40 |
| Optical Instruments | 40 |
| Thin Lenses & Lens Formula | 39 |
| Combination of Thin Lenses | 39 |
| Lens Maker's Formula & Power of Lens | 38 |
| Total Internal Reflection & Optical Fibres | 29 |
| Refraction at Spherical Surfaces | 28 |
| Refraction at Plane Surfaces & Refractive Index | 20 |
Questions students ask
Is Ray Optics important for NEET?
Very important — it is one of the highest-weightage chapters. Mirror/lens formula, refraction, TIR and prism problems are tested every year with 2-3 questions.
Which topics should I revise first?
Master mirror and lens formulas with sign convention, Snell's law and TIR, thin prism formula, lens combinations (1/f = 1/f₁ + 1/f₂), and microscope/telescope magnification.
How many questions from this chapter are on RankUp?
The RankUp app has 601 questions on Ray Optics and Optical Instruments, including 229 ELITE questions. Every question has a detailed explanation.
