📘 Light – Reflection and Refraction (Class 10 Science)

🔹 Part 2: Questions 26–50

Q26. The absolute refractive index of a medium is always:

A) Greater than 1
B) Less than 1
C) Equal to 0
D) Infinite

Correct Answer: A) Greater than 1

Explanation:

• ✅ A) Since speed in medium < speed in vacuum → n > 1.
• B) Less than 1 → Not possible.
• C, D → Physically incorrect.

Q27. When a ray of light travels from air into glass, its speed:

A) Increases
B) Decreases
C) Remains unchanged
D) Becomes infinite

Correct Answer: B) Decreases

Explanation:

• ✅ B) Glass is denser → Light slows down.
• A) Wrong, it speeds up only when going from denser to rarer.
• C, D → Not correct.

Q28. Which type of lens is used in magnifying glass?

A) Concave lens
B) Convex lens
C) Plano-concave lens
D) Concavo-convex lens

Correct Answer: B) Convex lens

Explanation:

• ✅ B) Convex lens → Used to magnify small objects.
• A) Concave → Always forms diminished images.
• C, D → Not used as magnifying glass.

Q29. When light enters from rarer to denser medium, the refracted ray:

A) Moves away from normal
B) Bends towards normal
C) Emerges undeviated
D) Disappears

Correct Answer: B) Bends towards normal

Explanation:

• ✅ B) Speed decreases in denser medium → Bends towards normal.
• A) Away → For denser to rarer.
• C, D → Not correct.

Q30. Which of the following is true about convex lenses?

A) Always forms real images
B) Always forms virtual images
C) Can form both real and virtual images
D) Never forms images

Correct Answer: C) Can form both real and virtual images

Explanation:

• ✅ C) Convex → Real (for object beyond focus) & Virtual (for object inside focus).
• A, B, D → Not universally true.

Q31. The power of a concave lens is:

A) Positive
B) Negative
C) Zero
D) Either positive or negative

Correct Answer: B) Negative

Explanation:

• ✅ B) Concave → Diverging lens, power negative.
• A) Positive → Convex.
• C, D → Wrong.

Q32. The SI unit of power of a lens is:

A) Watt
B) Dioptre
C) Hertz
D) Newton

Correct Answer: B) Dioptre

Explanation:

• ✅ B) 1 Dioptre = power of lens with focal length 1 m.
• A, C, D → Units of other quantities.

Q33. A convex lens with focal length 25 cm has power:

A) +2 D
B) +3 D
C) +4 D
D) +5 D

Correct Answer: C) +4 D

Explanation:

• P = 100/f (cm). f = 25 cm → P = 100/25 = 4D.
• ✅ C) +4 D (positive since convex lens).

Q34. The phenomenon of light returning into the same medium after striking a boundary is:

A) Refraction
B) Reflection
C) Dispersion
D) Scattering

Correct Answer: B) Reflection

Explanation:

• ✅ B) Reflection = Bouncing back of light.
• A, C, D → Other phenomena.

Q35. Which of the following surfaces obeys the laws of reflection?

A) Plane mirror
B) Curved mirror
C) Polished metal
D) All of these

Correct Answer: D) All of these

Explanation:

• ✅ D) All polished/reflecting surfaces obey reflection laws.
• A, B, C → Specific examples.

Q36. The principal focus of a convex lens is:

A) Point where rays appear to diverge
B) Point where rays parallel to axis converge
C) Midpoint of lens
D) Optical centre

Correct Answer: B) Point where rays parallel to axis converge

Explanation:

• ✅ B) Definition of principal focus of convex lens.
• A) For concave lens.
• C, D → Not correct.

Q37. The mirror used as a rear-view mirror in vehicles is:

A) Plane mirror
B) Concave mirror
C) Convex mirror
D) Cylindrical mirror

Correct Answer: C) Convex mirror

Explanation:

• ✅ C) Convex → Wide field of view, always erect images.
• A, B, D → Not used for rear-view.

Q38. When the object is at focus of a concave lens, the image formed is:

A) At infinity
B) Virtual and erect
C) At centre of curvature
D) Real and inverted

Correct Answer: B) Virtual and erect

Explanation:

• ✅ B) Concave lens → Always virtual, erect, diminished, irrespective of position.
• A, C, D → Not possible.

Q39. A ray of light parallel to the principal axis of a concave mirror passes through:

A) Focus
B) Centre of curvature
C) Pole
D) Optical centre

Correct Answer: A) Focus

Explanation:

• ✅ A) By law of reflection in spherical mirrors.
• B, C, D → Wrong points.

Q40. Which of the following is an optical device using reflection?

A) Lens
B) Prism
C) Kaleidoscope
D) Magnifying glass

Correct Answer: C) Kaleidoscope

Explanation:

• ✅ C) Kaleidoscope → Uses reflection by mirrors.
• A, B, D → Work mainly on refraction.

Q41. The focal length of a convex lens is 20 cm. The power is:

A) +2 D
B) +5 D
C) +4 D
D) +3 D

Correct Answer: B) +5 D

Explanation:

• P = 100/f (cm). f = 20 cm → 100/20 = 5 D.
• ✅ +5 D.

Q42. The relation between focal length (f) and radius of curvature (R) is:

A) f = R
B) f = R/2
C) f = 2R
D) f = R²

Correct Answer: B) f = R/2

Explanation:

• ✅ B) Always R = 2f.
• Others → Incorrect relations.

Q43. A virtual, erect, magnified image is obtained by concave mirror when object is placed:

A) Between focus and pole
B) At focus
C) At centre of curvature
D) Beyond centre of curvature

Correct Answer: A) Between focus and pole

Explanation:

• ✅ A) Concave mirror close to object → Magnified, virtual image.
• B, C, D → Real images.

Q44. Which device uses total internal reflection?

A) Plane mirror
B) Concave lens
C) Optical fibre
D) Magnifying glass

Correct Answer: C) Optical fibre

Explanation:

• ✅ C) Works on principle of TIR.
• A, B, D → Not related.

Q45. The refractive index of diamond is about:

A) 1.5
B) 2.42
C) 1.33
D) 1.0

Correct Answer: B) 2.42

Explanation:

• ✅ B) Diamond has highest refractive index among common materials.
• A = Glass, C = Water, D = Vacuum.

Q46. If refractive index of water is 1.33, speed of light in water is (c = 3×10⁸ m/s):

A) 2.25×10⁸ m/s
B) 3.0×10⁸ m/s
C) 1.5×10⁸ m/s
D) 1.0×10⁸ m/s

Correct Answer: A) 2.25×10⁸ m/s

Explanation:

• v = c/n = 3×10⁸ / 1.33 ≈ 2.25×10⁸ m/s.
• ✅ A.

Q47. A convex lens can be used as:

A) Microscope
B) Camera lens
C) Projector lens
D) All of these

Correct Answer: D) All of these

Explanation:

• ✅ D) Convex lens widely used in optical devices.
• A, B, C → Specific uses.

Q48. When an object is placed between focus and optical centre of convex lens, the image formed is:

A) Real, inverted, diminished
B) Real, inverted, enlarged
C) Virtual, erect, magnified
D) Virtual, inverted, diminished

Correct Answer: C) Virtual, erect, magnified

Explanation:

• ✅ C) Acts as magnifying glass.
• A, B → Real images.
• D → Not possible.

Q49. The phenomenon of light splitting into different colours is called:

A) Refraction
B) Dispersion
C) Reflection
D) Interference

Correct Answer: B) Dispersion

Explanation:

• ✅ B) Dispersion = Splitting of white light into spectrum.
• A, C, D → Different phenomena.

Q50. Which of the following is correct for plane mirrors?

A) Image is real and inverted
B) Image is virtual and erect
C) Image is always diminished
D) Image is always magnified

Correct Answer: B) Image is virtual and erect

Explanation:

• ✅ B) Plane mirrors → Always virtual, erect, same size.
• A, C, D → Incorrect.

Light Reflection Refraction MCQs, Class 10 Science Questions, NCERT Class 10 Science, CBSE Board Exam Practice, Online Learning Science, Light reflection and refraction class 10 science MCQs with answers, CBSE class 10 board exam important light chapter questions, NCERT syllabus-based light reflection and refraction practice questions, Online learning quiz on light reflection and refraction class 10, Important MCQs on light chapter for CBSE class 10 science