Optics is a vital part of the Class 12 Physics syllabus, covering reflection, refraction, lenses, mirrors, interference, diffraction, and polarization. These topics carry significant marks in the board exam and also form the foundation for competitive exams like JEE Main and NEET.
To help you prepare better, here’s a complete model paper prepared according to the latest CBSE exam pattern (2025). It includes 75 objective questions, 5 short answer questions, and 5 long answer questions — each designed to strengthen conceptual clarity.
Class 12 Physics Optics Model Paper 2025 | 75 Objective, Short & Long Questions with Answers
Section A: Objective Type Questions (1 Mark Each)
Q1. The speed of light in vacuum is:
A) 3×106 m/s3 \times 10^6 \, m/s
B) 3×108 m/s3 \times 10^8 \, m/s
C) 3×1010 m/s3 \times 10^{10} \, m/s
D) 3×105 m/s3 \times 10^5 \, m/s
Answer: B) 3×108 m/s3 \times 10^8 \, m/s
Q2. The refractive index of water is approximately:
A) 1.00
B) 1.33
C) 1.50
D) 2.00
Answer: B) 1.33
Q3. The focal length of a plane mirror is:
A) Zero
B) One metre
C) Infinity
D) Unity
Answer: C) Infinity
Q4. Which mirror converges parallel rays to a point?
A) Convex mirror
B) Plane mirror
C) Concave mirror
D) None
Answer: C) Concave mirror
Q5. The unit of power of a lens is:
A) Newton
B) Joule
C) Dioptre
D) Tesla
Answer: C) Dioptre
Q6. The lens thicker at the centre than at the edges is:
A) Concave lens
B) Convex lens
C) Plano-concave lens
D) Cylindrical lens
Answer: B) Convex lens
Q7. The mirror used by dentists is:
A) Plane mirror
B) Concave mirror
C) Convex mirror
D) Spherical mirror
Answer: B) Concave mirror
Q8. The mirror used as a rear-view mirror in vehicles is:
A) Plane mirror
B) Convex mirror
C) Concave mirror
D) Cylindrical mirror
Answer: B) Convex mirror
Q9. The mirror formula is:
A) v=u+fv = u + f
B) f=uvu+vf = \frac{uv}{u+v}
C) 1f=1v+1u\frac{1}{f} = \frac{1}{v} + \frac{1}{u}
D) None
Answer: C) 1f=1v+1u\frac{1}{f} = \frac{1}{v} + \frac{1}{u}
Q10. The power of a convex lens is:
A) Negative
B) Positive
C) Zero
D) Infinite
Answer: B) Positive
Q11. The power of a concave lens is:
A) Positive
B) Negative
C) Zero
D) Infinite
Answer: B) Negative
Q12. The relation between focal length and radius of curvature is:
A) f=Rf = R
B) f=R/2f = R/2
C) f=2Rf = 2R
D) f=R2f = R^2
Answer: B) f=R/2f = R/2
Q13. The bending of light when it passes from one medium to another is called:
A) Reflection
B) Refraction
C) Diffraction
D) Interference
Answer: B) Refraction
Q14. Snell’s law relates to:
A) Reflection
B) Refraction
C) Diffraction
D) Polarization
Answer: B) Refraction
Q15. When a ray travels from denser to rarer medium and angle of incidence exceeds the critical angle, the phenomenon is:
A) Reflection
B) Refraction
C) Total Internal Reflection
D) Dispersion
Answer: C) Total Internal Reflection
Q16. The critical angle for glass–air interface is approximately:
A) 30°
B) 42°
C) 60°
D) 90°
Answer: B) 42°
Q17. The color with the shortest wavelength is:
A) Red
B) Violet
C) Yellow
D) Green
Answer: B) Violet
Q18. The color that deviates least in a prism is:
A) Red
B) Blue
C) Violet
D) Green
Answer: A) Red
Q19. Splitting of white light into its component colors is known as:
A) Reflection
B) Diffraction
C) Dispersion
D) Scattering
Answer: C) Dispersion
Q20. Twinkling of stars is due to:
A) Scattering
B) Reflection
C) Atmospheric Refraction
D) Diffraction
Answer: C) Atmospheric Refraction
Q21. A convex mirror always forms an image that is:
A) Real and inverted
B) Virtual and erect
C) Real and diminished
D) None
Answer: B) Virtual and erect
Q22. The lens formula is:
A) v=u+fv = u + f
B) 1f=1v−1u\frac{1}{f} = \frac{1}{v} – \frac{1}{u}
C) f=uvu+vf = \frac{uv}{u+v}
D) f=u−vf = u – v
Answer: B) 1f=1v−1u\frac{1}{f} = \frac{1}{v} – \frac{1}{u}
Q23. The unit of focal length is:
A) Watt
B) Meter
C) Dioptre
D) Second
Answer: B) Meter
Q24. The magnification of a mirror is:
A) vu\frac{v}{u}
B) uv\frac{u}{v}
C) −vu-\frac{v}{u}
D) 11
Answer: C) −vu-\frac{v}{u}
Q25. Power of a lens is the reciprocal of:
A) Radius
B) Focal length (in metre)
C) Magnification
D) Wavelength
Answer: B) Focal length
Q26. A convex lens has focal length 50 cm. Its power is:
A) +2 D
B) +1 D
C) +0.5 D
D) -2 D
Answer: C) +2 D (since P=1/f=1/0.5=2DP=1/f=1/0.5=2D)
Q27. The refractive index of a medium depends on:
A) Wavelength of light
B) Nature of medium
C) Temperature
D) All of these
Answer: D) All of these
Q28. Which phenomenon proves wave nature of light?
A) Reflection
B) Refraction
C) Interference
D) Scattering
Answer: C) Interference
Q29. The device used to measure wavelength of light is:
A) Voltmeter
B) Spectrometer
C) Microscope
D) Telescope
Answer: B) Spectrometer
Q30. The scientist who proved wave nature of light:
A) Newton
B) Thomas Young
C) Planck
D) Einstein
Answer: B) Thomas Young
Q31. The formula for fringe width in Young’s Double Slit Experiment is:
A) β=dD\beta = \frac{d}{D}
B) β=λDd\beta = \frac{\lambda D}{d}
C) β=Dλd\beta = \frac{D}{\lambda d}
D) None
Answer: B) β=λDd\beta = \frac{\lambda D}{d}
Q32. Light waves are:
A) Longitudinal
B) Transverse
C) Scalar
D) Longitudinal and Transverse
Answer: B) Transverse
Q33. Polarization can occur only in:
A) Transverse waves
B) Longitudinal waves
C) Sound waves
D) All
Answer: A) Transverse waves
Q34. The process of restricting light vibrations to a single plane is:
A) Reflection
B) Polarization
C) Refraction
D) Interference
Answer: B) Polarization
Q35. The device that works on total internal reflection is:
A) Periscope
B) Kaleidoscope
C) Optical Fiber
D) Telescope
Answer: C) Optical Fiber
Q36. A rainbow is formed due to:
A) Diffraction
B) Interference
C) Dispersion and Reflection
D) Polarization
Answer: C) Dispersion and Reflection
Q37. The power of a combination of two lenses is:
A) P=P1+P2P = P_1 + P_2
B) P=P1−P2P = P_1 – P_2
C) P=P1/P2P = P_1 / P_2
D) P=P1P2P = P_1 P_2
Answer: A) P=P1+P2P = P_1 + P_2
Q38. Which lens is used as a magnifying glass?
A) Concave lens
B) Convex lens
C) Plano-concave
D) Cylindrical lens
Answer: B) Convex lens
Q39. The least distance of distinct vision for a normal eye is:
A) 10 cm
B) 15 cm
C) 25 cm
D) 50 cm
Answer: C) 25 cm
Q40. The phenomenon responsible for blue color of the sky is:
A) Scattering
B) Reflection
C) Dispersion
D) Refraction
Answer: A) Scattering
Q41. The wavelength of visible light is between:
A) 100–200 nm
B) 400–700 nm
C) 1–10 µm
D) 700–1000 nm
Answer: B) 400–700 nm
Q42. The focal length of a mirror is half of:
A) Aperture
B) Radius of curvature
C) Object distance
D) Image distance
Answer: B) Radius of curvature
Q43. The image formed by a plane mirror is:
A) Real and inverted
B) Virtual and erect
C) Real and erect
D) Enlarged
Answer: B) Virtual and erect
Q44. The equation sinisinr=n\frac{\sin i}{\sin r} = n represents:
A) Newton’s Law
B) Snell’s Law
C) Ohm’s Law
D) Gauss’s Law
Answer: B) Snell’s Law
Q45. Which color of light has maximum speed in glass?
A) Red
B) Blue
C) Green
D) Violet
Answer: A) Red
Q46. For small angle of prism, deviation δ is given by:
A) δ=(n−1)A\delta = (n-1)A
B) δ=nA\delta = nA
C) δ=(A−1)n\delta = (A-1)n
D) δ=A/n\delta = A/n
Answer: A) δ=(n−1)A\delta = (n-1)A
Q47. Light is a form of:
A) Sound wave
B) Mechanical wave
C) Electromagnetic wave
D) Matter wave
Answer: C) Electromagnetic wave
Q48. The law of reflection states:
A) Angle of incidence = Angle of reflection
B) Angle of incidence < Angle of reflection
C) Both equal to 90°
D) None
Answer: A) Angle of incidence = Angle of reflections
Q49. The eye lens is:
A) Concave
B) Convex
C) Plane
D) None
Answer: B) Convex
Q50. The ability of the eye lens to adjust its focal length is called:
A) Adaptation
B) Accommodation
C) Reflection
D) Dispersion
Answer: B) Accommodation
Q51. The image formed by a concave mirror for an object between focus and pole is:
A) Real and inverted
B) Virtual and erect
C) Diminished and real
D) None
Answer: B) Virtual and erect
Q52. The path of light in the same medium is always:
A) Curved
B) Straight
C) Random
D) Circular
Answer: B) Straight
Q53. The intensity of light is proportional to:
A) Frequency
B) Square of amplitude
C) Velocity
D) None
Answer: B) Square of amplitude
Q54. The type of mirror used in headlights of a car is:
A) Plane mirror
B) Convex mirror
C) Concave mirror
D) None
Answer: C) Concave mirror
Q55. For refraction, frequency of light:
A) Changes
B) Remains same
C) Becomes double
D) Becomes half
Answer: B) Remains same
Q56. The refractive index is always:
A) Greater than 1
B) Less than 1
C) Equal to 1
D) Infinite
Answer: A) Greater than 1
Q57. The mirror used in solar furnaces is:
A) Plane mirror
B) Convex mirror
C) Concave mirror
D) Parabolic mirror
Answer: D) Parabolic mirror
Q58. Dispersion takes place because:
A) Different colors travel with same speed
B) Different colors travel with different speeds
C) Light bends equally
D) None
Answer: B) Different colors travel with different speeds
Q59. The focal length of a convex lens in water becomes:
A) Increases
B) Decreases
C) Same
D) Zero
Answer: A) Increases
Q60. Which optical phenomenon is used in mirage?
A) Reflection
B) Total Internal Reflection
C) Diffraction
D) Scattering
Answer: B) Total Internal Reflection
Q61. A ray of light incident at 90° on a surface:
A) Reflects back
B) Refracts normally
C) Deviates
D) None
Answer: B) Refracts normally
Q62. In double-slit experiment, if slit separation increases, fringe width:
A) Increases
B) Decreases
C) Unchanged
D) Doubles
Answer: B) Decreases
Q63. The device based on interference of light is:
A) Newton’s Ring
B) Telescope
C) Microscope
D) Photometer
Answer: A) Newton’s Ring
Q64. The phase difference between two waves for destructive interference is:
A) 0
B) π/2\pi/2
C) π\pi
D) 2π2\pi
Answer: C) π\pi
Q65. The angular resolution of a telescope depends on:
A) Wavelength
B) Diameter of objective lens
C) Both A and B
D) None
Answer: C) Both A and B
Q66. Diffraction occurs when:
A) Light passes through a narrow slit
B) Light reflects
C) Light refracts
D) Light absorbs
Answer: A) Light passes through a narrow slit
Q67. Which color of light is scattered the most?
A) Red
B) Blue
C) Green
D) Yellow
Answer: B) Blue
Q68. The image formed by a convex lens of a distant object is:
A) Virtual
B) Real and inverted
C) Erect
D) None
Answer: B) Real and inverted
Q69. A virtual image is always formed:
A) On same side as object
B) On opposite side
C) At infinity
D) None
Answer: A) On same side as object
Q70. Which of the following has negative focal length?
A) Concave mirror
B) Convex mirror
C) Convex lens
D) None
Answer: B) Convex mirror
Q71. Light travels fastest in:
A) Air
B) Water
C) Glass
D) Diamond
Answer: A) Air
Q72. The power of a plane mirror is:
A) Positive
B) Negative
C) Zero
D) Infinite
Answer: C) Zero
Q73. The radius of curvature of plane mirror is:
A) Zero
B) Infinite
C) One
D) Two
Answer: B) Infinite
Q74. The minimum deviation position in a prism occurs when:
A) i = e
B) i > e
C) i < e
D) None
Answer: A) i = e
Q75. Which of the following is not an optical instrument?
A) Periscope
B) Microscope
C) Galvanometer
D) Telescope
Answer: C) Galvanometer
Section B: Short Answer Questions (2–3 Marks Each)
Q1. State and explain Snell’s Law.
Answer:
Snell’s Law states that the ratio of the sine of the angle of incidence to the sine of the angle of refraction is constant for a given pair of media.
sinisinr=n21\frac{\sin i}{\sin r} = n_{21}
where n21n_{21} is the refractive index of the second medium with respect to the first.
Q2. Define focal length and radius of curvature of a mirror.
Answer:
The focal length (f) is the distance between the pole and the focus of the mirror.
The radius of curvature (R) is the distance between the pole and the center of curvature. For spherical mirrors, R=2fR = 2f.
Q3. What is meant by total internal reflection?
Answer:
When light passes from a denser to a rarer medium and the angle of incidence exceeds the critical angle, it reflects entirely back into the denser medium. This is called Total Internal Reflection (TIR).
Q4. Why does the sky appear blue?
Answer:
Due to Rayleigh scattering, shorter wavelengths (blue light) scatter more than longer wavelengths (red light) when sunlight interacts with air molecules, making the sky appear blue.
Q5. Write two differences between reflection and refraction.
Answer:
| Reflection | Refraction |
|---|---|
| Light bounces back into the same medium | Light bends into another medium |
| Follows law of reflection | Follows Snell’s law |
Section C: Long Answer Questions (5 Marks Each)
Q1. Derive the mirror formula.
Answer:
Consider a concave mirror with object distance uu, image distance vv, and focal length ff.
By geometry and sign convention,
1f=1v+1u\frac{1}{f} = \frac{1}{v} + \frac{1}{u}
This relation holds for all spherical mirrors, linking focal length, image distance, and object distance.
Q2. Explain the formation of images by a convex lens with ray diagrams for various object positions.
Answer:
A convex lens can form real and virtual images depending on object distance:
-
Beyond 2F: Image between F and 2F, real, inverted, smaller.
-
At 2F: Image at 2F, same size, real, inverted.
-
Between F and 2F: Image beyond 2F, real, inverted, magnified.
-
At F: Image at infinity.
-
Between F and O: Virtual, erect, magnified.
Q3. Describe Young’s Double Slit Experiment and derive the expression for fringe width.
Answer:
In YDSE, light from two coherent slits interferes on a screen to form bright and dark fringes.
Fringe width,
β=λDd\beta = \frac{\lambda D}{d}
where λ\lambda = wavelength, DD = distance of screen, dd = slit separation.
Bright and dark fringes result from constructive and destructive interference.
Q4. Explain the principle and working of a simple microscope.
Answer:
A simple microscope is a convex lens used to magnify small objects placed between the focus and lens. It forms a virtual, erect, and magnified image on the same side of the lens.
Magnifying power M=1+DfM = 1 + \frac{D}{f}, where D = least distance of distinct vision.
Q5. Discuss polarization of light and its applications.
Answer:
Polarization is the phenomenon of restricting vibrations of light to a single plane.
Methods: Reflection, refraction, or using polarizing filters.
Applications:
-
Sunglasses to reduce glare
-
LCD screens
-
Stress analysis in transparent materials
-
3D movie glasses
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