Ray Optics and Optical Instruments Class 12 Physics MCQs 2026-27 | Chapter 9

CBSE Class 12 Physics • Chapter 9 • 2026–27

Ray Optics and Optical Instruments — MCQs with Answers

Class 12 Physics Chapter 9 MCQs for CBSE 2026–27 covering mirrors, refraction, total internal reflection, optical fibres, spherical surfaces, lenses, prism, microscopes and telescopes.

Study sequence: Revise the Chapter 9 Complete Notes, then use the Chapter 9 Important Questions for written practice. Use this MCQ set to test concept recognition, formula selection, sign convention and application.

Quick Answer — What do these MCQs test?

This set tests the current Chapter 9 scope through 80 MCQs, including conceptual, formula-based, numerical, application and reasoning questions. The questions are arranged from core concepts to mixed and challenge-level reasoning.

These are practice questions created for revision. They are not claims about the exact questions that will appear in the CBSE board examination.

1. Current CBSE 2026–27 Scope

The current CBSE syllabus for Chapter 9 includes reflection and spherical mirrors; refraction; total internal reflection and optical fibres; refraction at spherical surfaces; lenses; thin-lens formula; lens-maker's formula; magnification; power; combinations of thin lenses in contact; prism; microscopes; and astronomical telescopes, both reflecting and refracting, with their magnifying powers.

Official CBSE Physics Curriculum 2026–27

Editorial note: The page structure combines common search intents found across established Class 12 Ray Optics MCQ resources—MCQs with answers, explanations, numerical application, exam-oriented practice and difficulty progression—while the syllabus boundary is controlled by the official CBSE 2026–27 curriculum.

2. How to Use These MCQs

Round 1 Attempt without looking at the answer.

Round 2 For every wrong answer, identify whether the error was conceptual, formula-based, sign-convention based or calculation based.

Round 3 Reattempt only the wrong questions after revising the relevant Notes section.

Suggested self-check only: 60+ indicates that you are ready for another practice format; 45–59 means targeted revision may help; below 45 is a signal to revisit the Notes and retry the weak sections.

CBSE 2026–27 Question-Skill Alignment

The official Physics curriculum describes the 70-mark theory paper across remembering/understanding, applying, and higher-order analysing/evaluating/creating skills. This MCQ page therefore includes direct recall as well as formula selection, numerical application and reasoning questions. The distribution below is a feature of the overall theory design, not a prediction of how many Chapter 9 MCQs will appear.

Official skill category	Approx. share of theory marks	How this page responds
Remembering + Understanding	38%	Definitions, laws, signs, image nature and core formula recognition.
Applying	32%	Numerical MCQs, formula substitution and optical-system applications.
Analysing + Evaluating + Creating	30%	Reasoning, comparison, boundary cases and multi-step conceptual choices.

NCERT Exemplar Problems — Physics Unit 9: Ray Optics and Optical Instruments

3. Reflection and Spherical Mirrors

1. The angle of reflection from a plane mirror is measured with respect to the:

A. mirror surface

B. normal at the point of incidence

C. principal axis only

D. incident ray

Answer: B

Angles of incidence and reflection are measured from the normal.

2. For a spherical mirror, the relation between focal length f and radius of curvature R is:

A. R = f

B. R = 2f

C. R = f/2

D. R = 4f

Answer: B

For a spherical mirror, the paraxial focal length is half the radius of curvature.

3. Under the Cartesian sign convention, the focal length of a concave mirror is:

A. positive

B. negative

C. zero

D. always infinite

Answer: B

The principal focus of a concave mirror lies on the negative x-axis for the usual incident-light direction.

4. An object is placed beyond C of a concave mirror. Its image is formed:

A. between F and C

B. at C

C. beyond C

D. between P and F

Answer: A

A real, inverted and diminished image forms between F and C.

5. When an object is placed between F and C of a concave mirror, the image is:

A. virtual and diminished

B. real and magnified beyond C

C. real and diminished between F and C

D. virtual and magnified behind the mirror

Answer: B

The image is real, inverted and enlarged beyond C.

6. A convex mirror always forms, for a real object:

A. a real inverted image

B. a real magnified image

C. a virtual, erect and diminished image

D. a virtual inverted image

Answer: C

The image is behind the mirror, erect and smaller than the object.

7. The mirror formula is:

A. 1/f = 1/u + 1/v

B. 1/f = 1/v − 1/u

C. 1/f = 1/u − 1/v

D. f = u + v

Answer: A

Using the Cartesian convention, 1/f = 1/v + 1/u.

8. The magnification produced by a spherical mirror is:

A. m = v/u

B. m = −v/u

C. m = u/v

D. m = f/u

Answer: B

For mirrors, magnification m = hᵢ/hₒ = −v/u.

9. If magnification by a mirror is negative, the image is:

A. erect

B. inverted

C. necessarily virtual

D. necessarily diminished

Answer: B

Negative transverse magnification denotes an inverted image.

10. A ray parallel to the principal axis of a concave mirror, after reflection, passes through:

A. the pole

B. the centre of curvature

C. the principal focus

D. the midpoint of the mirror

Answer: C

A paraxial ray parallel to the axis is reflected through F.

4. Refraction, Refractive Index and TIR

11. Snell's law for refraction between two media is:

A. n₁ cos i = n₂ cos r

B. n₁ sin i = n₂ sin r

C. n₁ tan i = n₂ tan r

D. n₁i = n₂r

Answer: B

Snell's law relates the refractive indices and sines of the angles.

12. When light enters a denser medium obliquely from a rarer medium, it generally bends:

A. away from the normal

B. towards the normal

C. along the surface

D. without changing direction

Answer: B

Its speed decreases and the ray bends towards the normal.

13. When light passes from air into glass, its frequency:

A. increases

B. decreases

C. remains unchanged

D. becomes zero

Answer: C

Frequency is fixed by the source; the medium changes speed and wavelength.

14. The absolute refractive index of a medium is defined as:

A. v/c

B. c/v

C. λ/c

D. cλ

Answer: B

n = c/v for a transparent medium.

15. For light travelling from a denser medium to air, total internal reflection is possible when the angle of incidence is:

A. less than the critical angle

B. equal to zero only

C. greater than the critical angle

D. always 90°

Answer: C

Both conditions are required: denser-to-rarer travel and i > C.

16. For a medium of refractive index n with respect to air, the critical-angle relation is:

A. sin C = n

B. cos C = 1/n

C. sin C = 1/n

D. tan C = n

Answer: C

For a denser medium to air, n = 1/sin C.

17. An optical fibre primarily works on:

A. diffraction

B. interference

C. total internal reflection

D. polarisation

Answer: C

Light is guided mainly by repeated total internal reflection in the core.

18. For an optical fibre, the refractive index of the core is generally:

A. less than that of the cladding

B. greater than that of the cladding

C. equal to zero

D. unrelated to the cladding

Answer: B

A higher core refractive index enables the required internal reflection at the core-cladding boundary.

19. If the speed of light in a medium decreases while frequency remains unchanged, its wavelength:

A. increases

B. decreases

C. remains unchanged

D. becomes infinite

Answer: B

Since v = fλ and f remains constant, λ decreases when v decreases.

20. At normal incidence on a plane refracting surface, the ray:

A. always undergoes TIR

B. bends by 90°

C. continues without angular deviation

D. is completely reflected

Answer: C

At i = 0°, the refracted ray follows the normal, so there is no angular deviation.

5. Refraction at Spherical Surfaces and Lenses

21. The thin-lens formula in the Cartesian convention is:

A. 1/f = 1/v + 1/u

B. 1/f = 1/v − 1/u

C. 1/f = 1/u − 1/v

D. 1/f = uv

Answer: B

For a thin lens, 1/f = 1/v − 1/u.

22. For a convex lens in air, the focal length is:

A. negative

B. positive

C. zero

D. undefined

Answer: B

A converging convex lens has a positive focal length in air.

23. For a concave lens in air, the power is:

A. positive

B. negative

C. zero

D. always 1 D

Answer: B

A concave lens has negative focal length, so P = 1/f is negative.

24. The SI unit of lens power is:

A. tesla

B. dioptre

C. metre per second

D. newton

Answer: B

Power is measured in dioptres (D), equivalent to m⁻¹.

25. A lens of focal length 0.5 m has power:

A. +0.5 D

B. +2 D

C. −2 D

D. +5 D

Answer: B

P = 1/f = 1/0.5 = +2 D.

26. Two thin lenses of powers P₁ and P₂ are in contact. Their equivalent power is:

A. P₁P₂

B. P₁/P₂

C. P₁ + P₂

D. P₁ − P₂ only

Answer: C

For thin lenses in contact, powers add algebraically.

27. A convex lens forms a real, inverted and diminished image when the object is placed:

A. between F and 2F

B. at F

C. beyond 2F

D. between O and F

Answer: C

For u beyond 2F, the image lies between F and 2F and is diminished.

28. A convex lens forms a virtual, erect and magnified image when the object is placed:

A. beyond 2F

B. at 2F

C. between F and O

D. at infinity

Answer: C

A convex lens behaves as a magnifier when the object is within its focal length.

29. A concave lens for a real object normally forms an image that is:

A. real and inverted

B. virtual, erect and diminished

C. real and magnified

D. virtual and inverted

Answer: B

A concave lens is diverging and produces a virtual, erect, diminished image.

30. The general lens-maker relation for a thin lens in a medium is best written as:

A. 1/f = (n_lens/n_medium − 1)(1/R₁ − 1/R₂)

B. 1/f = n_medium(1/R₁ + 1/R₂)

C. 1/f = R₁R₂

D. f = n_lens/R₁

Answer: A

The focal length depends on relative refractive index and surface curvatures.

31. If the focal length of a converging lens is decreased, its power:

A. decreases

B. increases

C. becomes zero

D. changes sign automatically

Answer: B

P = 1/f, so a smaller positive focal length means larger positive power.

32. A lens immersed in a medium whose refractive index approaches that of the lens material tends to have:

A. a very small focal length

B. a very large focal length

C. unchanged power

D. infinite power

Answer: B

The relative refractive index approaches 1, reducing the lens's refracting power and increasing focal length.

6. Prism

33. The angle between the two refracting faces of a prism is called:

A. angle of deviation

B. angle of prism

C. critical angle

D. angle of incidence

Answer: B

A is the prism angle between its two refracting faces.

34. At minimum deviation through a prism:

A. i = 0

B. e = 0

C. i = e

D. r₁ = 0

Answer: C

The path is symmetric at minimum deviation, so i = e and r₁ = r₂ = A/2.

35. At minimum deviation, the refractive index of a prism is given by:

A. n = sin(A/2)/sin((A+δm)/2)

B. n = sin((A+δm)/2)/sin(A/2)

C. n = A/δm

D. n = δm/A

Answer: B

This is the standard minimum-deviation relation.

36. At minimum deviation, the angle of refraction inside each face is:

A. A

B. A/2

C. 2A

D. δm/2

Answer: B

Symmetry gives r₁ = r₂ and r₁ + r₂ = A.

37. The deviation produced by a prism is the angle between:

A. the incident ray and emergent ray

B. the two prism faces

C. the normal and incident ray only

D. the two normals only

Answer: A

Deviation measures the angular change between the original direction and emergent direction.

38. For a prism at minimum deviation, the emergent ray is:

A. asymmetric with the incident ray

B. parallel to the first face

C. symmetrically placed with respect to the prism

D. always normal to the second face

Answer: C

The optical path is symmetric at minimum deviation.

7. Microscopes and Telescopes

39. The objective of a compound microscope generally has:

A. large focal length

B. small focal length

C. zero focal length

D. negative aperture

Answer: B

A short-focal-length objective produces a strongly magnified intermediate image.

40. In a compound microscope, the objective first produces a:

A. final virtual image directly

B. magnified real intermediate image

C. diminished virtual image only

D. parallel beam at the eyepiece in every case

Answer: B

The objective forms a magnified real intermediate image that the eyepiece further magnifies.

41. The eyepiece of a compound microscope acts essentially as a:

A. plane mirror

B. simple magnifier

C. convex mirror

D. prism only

Answer: B

The eyepiece magnifies the intermediate image formed by the objective.

42. In a refracting astronomical telescope, the objective generally has:

A. shorter focal length than the eyepiece

B. longer focal length than the eyepiece

C. the same focal length in every design

D. zero focal length

Answer: B

Large objective focal length helps provide angular magnification and image formation suitable for distant objects.

43. The magnifying power of a refracting telescope in normal adjustment is:

A. fₑ/fₒ

B. −fₒ/fₑ

C. fₒ + fₑ

D. fₒfₑ

Answer: B

For normal adjustment, M = −fₒ/fₑ.

44. In normal adjustment of an astronomical telescope, the final image is formed:

A. at the objective

B. at the eyepiece surface

C. at infinity

D. at the least distance of distinct vision

Answer: C

Normal adjustment means the final image is at infinity for relaxed viewing.

45. A reflecting astronomical telescope uses a large:

A. convex lens as the primary collector

B. concave primary mirror

C. plane mirror only

D. concave lens

Answer: B

The primary mirror collects and focuses the incoming light.

46. One major optical advantage of a reflecting telescope is that a mirror:

A. must be made from a dispersive glass lens

B. does not suffer chromatic aberration due to refraction

C. cannot collect light

D. always has zero focal length

Answer: B

Reflection itself does not produce chromatic aberration of the kind associated with refracting lenses.

47. The angular magnification of an astronomical telescope depends primarily on:

A. ratio of objective and eyepiece focal lengths

B. sum of their powers only

C. mass of the telescope

D. diameter of the eyepiece alone

Answer: A

For normal adjustment, |M| = fₒ/fₑ.

8. Mixed Concept and Numerical MCQs

48. An object is placed 30 cm in front of a concave mirror of focal length 20 cm. Using the Cartesian convention, the image distance is:

A. −60 cm

B. +60 cm

C. −12 cm

D. +12 cm

Answer: A

With u = −30 cm and f = −20 cm, 1/v = 1/f − 1/u = −1/20 + 1/30 = −1/60, so v = −60 cm.

49. A convex lens of focal length 20 cm has an object at 30 cm. The image distance is:

A. +60 cm

B. −60 cm

C. +12 cm

D. −12 cm

Answer: A

With u = −30 cm and f = +20 cm, 1/v = 1/f + 1/u = 1/20 − 1/30 = 1/60, so v = +60 cm.

50. A lens of power −4 D has focal length:

A. +0.25 m

B. −0.25 m

C. +4 m

D. −4 m

Answer: B

f = 1/P = −0.25 m.

51. Two lenses of +5 D and −2 D are in contact. Their equivalent power is:

A. +7 D

B. +3 D

C. −3 D

D. −7 D

Answer: B

P = +5 + (−2) = +3 D.

52. A medium has refractive index 1.5 with respect to air. Its critical angle is closest to:

A. 19.5°

B. 41.8°

C. 60°

D. 75°

Answer: B

sin C = 1/1.5 = 2/3, giving C ≈ 41.8°.

53. If a ray in glass strikes the glass-air boundary at an angle smaller than the critical angle, it will:

A. undergo TIR

B. refract into air

C. stop completely

D. always travel along the boundary

Answer: B

TIR requires incidence greater than the critical angle.

54. A convex lens has focal length +25 cm. Its power is:

A. +0.25 D

B. +4 D

C. −4 D

D. +25 D

Answer: B

f = 0.25 m, so P = 1/0.25 = +4 D.

55. For a telescope with fₒ = 100 cm and fₑ = 5 cm, the magnitude of magnifying power in normal adjustment is:

A. 5

B. 20

C. 95

D. 105

Answer: B

|M| = fₒ/fₑ = 100/5 = 20.

56. At a plane refracting surface, which quantity is continuous across the boundary for a monochromatic light source?

A. frequency

B. speed

C. wavelength

D. refractive index

Answer: A

The frequency remains fixed; speed and wavelength depend on the medium.

57. If the focal length of a lens is expressed as 50 cm in the power formula without conversion, the numerical power obtained is wrong because:

A. power uses focal length in metres

B. power uses focal length in kilometres

C. power has no unit

D. focal length must always be negative

Answer: A

Power in dioptres is the reciprocal of focal length in metres.

58. At the optical centre of a thin lens, a ray is approximately:

A. reflected back

B. undeviated

C. refracted at 90°

D. always totally internally reflected

Answer: B

A paraxial ray through the optical centre of a thin lens is approximately undeviated.

59. A real image formed by a converging lens is generally:

A. erect

B. inverted

C. always virtual

D. always diminished

Answer: B

A real image from a single converging lens is inverted relative to the object.

60. Which pair contains only Chapter 9 core topics in the current CBSE 2026–27 syllabus?

A. TIR and optical fibres

B. Young's double-slit interference and diffraction

C. Photoelectric effect and de Broglie waves

D. Nuclear fission and binding energy

Answer: A

The current Chapter 9 syllabus explicitly includes TIR and optical fibres; the other options belong to other chapters.

9. Challenge MCQs — Application and Reasoning

61. A convex lens is immersed in a liquid having the same refractive index as the lens material. In the ideal thin-lens approximation, its optical power tends towards:

A. a large positive value

B. zero

C. a large negative value

D. infinity

Answer: B

When n_lens/n_medium approaches 1, the lens-maker factor approaches zero, so power tends towards zero.

62. At minimum deviation in a prism, if the prism angle is A, the two internal refraction angles are:

A. A and 0

B. A/2 and A/2

C. 2A and −A

D. A/3 and 2A/3

Answer: B

Symmetry gives r₁ = r₂ and r₁ + r₂ = A.

63. A student obtains a positive image distance for a thin convex lens under the Cartesian convention. This normally indicates the image is:

A. on the object side and virtual

B. on the opposite side and real

C. at the optical centre

D. necessarily diminished

Answer: B

For a real object, positive v corresponds to a real image on the positive side of the lens.

64. Which change increases the magnitude of the normal-adjustment magnifying power of a refracting telescope?

A. Increase fₑ while keeping fₒ fixed

B. Decrease fₒ while keeping fₑ fixed

C. Increase fₒ while keeping fₑ fixed

D. Make fₒ = fₑ

Answer: C

|M| = fₒ/fₑ, so increasing fₒ increases the magnitude.

65. A ray travels from glass to air at an incidence angle exactly equal to the critical angle. The refracted ray:

A. is totally reflected

B. emerges along the interface

C. returns along the incident path

D. has zero speed

Answer: B

At the critical angle, the refracted angle is 90°, so the refracted ray grazes the interface.

66. Which statement about a concave mirror is correct for an object between P and F?

A. Image is real and inverted

B. Image is virtual, erect and magnified

C. Image is real and diminished

D. Image is always at C

Answer: B

The reflected rays diverge and their backward extensions form a virtual, erect, magnified image behind the mirror.

67. If two thin lenses in contact have equal and opposite powers, the combination behaves ideally as:

A. a converging lens

B. a diverging lens

C. an afocal zero-power combination

D. a plane mirror

Answer: C

P = P₁ + P₂ = 0, so the equivalent focal length tends to infinity.

68. Which quantity is most directly responsible for the sign of lens power in air?

A. sign of focal length

B. mass of the lens

C. diameter alone

D. object height

Answer: A

P = 1/f, so the sign of power follows the sign of focal length.

69. For a real object viewed through a concave lens, the image is formed:

A. beyond 2F on the far side

B. between the optical centre and focus on the object side

C. at infinity

D. behind the lens as a real image

Answer: B

A concave lens produces a virtual image between O and F on the same side as the object.

70. A concave mirror has u = −30 cm and f = −20 cm. Its magnification is:

A. −2

B. +2

C. −1/2

D. +1/2

Answer: A

First, v = −60 cm from the mirror formula. Then m = −v/u = −(−60)/(−30) = −2.

9A. Board-Style Challenge Set — 71 to 80

71. A ray enters glass from air at an incidence angle of 30°. If the refractive index of glass is 1.5, the sine of the refracted angle is:

A. 0.75

B. 0.50

C. 0.33

D. 1.50

Answer: C

Snell's law gives sin r = sin 30°/1.5 = 0.5/1.5 = 1/3.

72. A convex lens has focal length 10 cm. An object is placed 15 cm from it. The image is formed:

A. 30 cm on the opposite side

B. 6 cm on the same side

C. 5 cm on the opposite side

D. at infinity

Answer: A

With u = −15 cm and f = +10 cm, 1/v = 1/10 − 1/15 = 1/30, so v = +30 cm.

73. If a concave mirror has focal length −12 cm, its radius of curvature is:

A. −6 cm

B. +6 cm

C. −24 cm

D. +24 cm

Answer: C

R = 2f = 2(−12 cm) = −24 cm.

74. A lens has power +5 D. If it is placed in a medium that reduces its effective optical power, its effective focal length will:

A. decrease

B. increase

C. become negative automatically

D. remain fixed in all media

Answer: B

Since P = 1/f, a reduction in positive power corresponds to an increase in positive focal length.

75. At minimum deviation in a prism, if A = 60° and δm = 40°, the refractive index is:

A. sin 20°/sin 50°

B. sin 50°/sin 30°

C. sin 30°/sin 50°

D. sin 60°/sin 40°

Answer: B

n = sin[(A + δm)/2]/sin(A/2) = sin 50°/sin 30°.

76. A telescope has objective focal length 150 cm and eyepiece focal length 5 cm. In normal adjustment, the magnitude of its angular magnifying power is:

A. 15

B. 25

C. 30

D. 155

Answer: C

|M| = fₒ/fₑ = 150/5 = 30.

77. Which statement correctly compares a real image and a virtual image?

A. A real image can always be seen only with a mirror

B. A real image can be formed on a screen; a virtual image cannot be formed on a screen in the same way

C. A virtual image is always inverted

D. A real image is always magnified

Answer: B

Real rays actually meet for a real image, allowing it to be received on a screen; virtual rays only appear to meet.

78. A light ray inside a denser medium reaches a boundary with a rarer medium at i = C. The angle of refraction is:

A. 0°

B. C

C. 90°

D. 180°

Answer: C

At the critical angle, the refracted ray grazes the interface, so r = 90°.

79. A pair of thin lenses in contact has equivalent power +2 D. Its equivalent focal length is:

A. +0.5 m

B. −0.5 m

C. +2 m

D. −2 m

Answer: A

f = 1/P = 1/2 = +0.5 m.

80. Which statement best describes why a reflecting telescope avoids chromatic aberration associated with refraction?

A. A mirror focuses light by reflection rather than wavelength-dependent refraction

B. A mirror has zero focal length

C. A mirror cannot form a real image

D. A mirror always has a smaller aperture

Answer: A

The chromatic aberration associated with dispersion in refracting lenses is avoided in a reflecting primary mirror.

10. High-Frequency Formula Check

Concept	Formula / relation to remember
Spherical mirror	1/f = 1/v + 1/u
Mirror magnification	m = −v/u
Refraction	n₁ sin i = n₂ sin r
Critical angle to air	sin C = 1/n
Thin lens	1/f = 1/v − 1/u
Lens magnification	m = v/u
Power	P = 1/f, with f in metres
Lenses in contact	P = P₁ + P₂
Prism at minimum deviation	n = sin[(A + δm)/2] / sin(A/2)
Refracting telescope, normal adjustment	M = −fₒ/fₑ

11. Quick Answers — Ray Optics & Optical Instruments

What is the mirror formula?
For a spherical mirror, 1/f = 1/v + 1/u.

What is the thin-lens formula?
For a thin lens, 1/f = 1/v − 1/u.

What are the conditions for total internal reflection?
Light must travel from an optically denser medium to a rarer medium, and the incidence angle must be greater than the critical angle.

What is lens power?
Power is the reciprocal of focal length in metres: P = 1/f, measured in dioptres.

What is magnifying power of a refracting telescope in normal adjustment?
M = −fₒ/fₑ.

12. Official CBSE Resources

CBSE Physics Curriculum 2026–27

CBSE Class XII 2026–27 Sample Question Papers & Marking Schemes

NCERT Physics Part-II Textbook Portal

The official CBSE Academics page currently lists Physics among the Class XII 2026–27 Sample Question Paper and Marking Scheme resources.

13. Final MCQ Revision Checklist

• ☐ I can apply the Cartesian sign convention consistently.
• ☐ I know the mirror and thin-lens equations.
• ☐ I can distinguish magnification from magnifying power.
• ☐ I can identify both conditions for total internal reflection.
• ☐ I can calculate critical angle and lens power.
• ☐ I can combine lens powers algebraically.
• ☐ I understand minimum deviation in a prism.
• ☐ I know the basic working and magnifying-power relations of microscopes and telescopes.
• ☐ I can diagnose my mistakes instead of memorising answer letters.

Continue your Chapter 9 study path: Complete Notes  →  Important Questions  →  MCQs