📘 Light – Reflection and Refraction (Class 10 Science)

🔹 Part 1: Questions 1–25

Q1. The phenomenon of bouncing back of light after striking a polished surface is called:

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

Correct Answer: C) Reflection

Explanation:

• A) Refraction → Bending of light in different medium.
• B) Dispersion → Splitting of white light into colours.
• ✅ C) Reflection → Bouncing back of light.
• D) Scattering → Spreading of light in atmosphere.

Q2. The angle between incident ray and normal is called:

A) Angle of reflection
B) Angle of incidence
C) Angle of deviation
D) Angle of prism

Correct Answer: B) Angle of incidence

Explanation:

• A) Reflection → Between reflected ray and normal.
• ✅ B) Incidence → Between incident ray and normal.
• C) Deviation → Change in path due to refraction.
• D) Prism angle → Geometry of prism.

Q3. The image formed by a plane mirror is always:

A) Real and inverted
B) Virtual and erect
C) Enlarged and real
D) Diminished and inverted

Correct Answer: B) Virtual and erect

Explanation:

• A) Real images → By concave mirrors.
• ✅ B) Plane mirror → Always virtual, erect, same size.
• C, D → Not applicable to plane mirrors.

Q4. The mirror used by dentists to see enlarged image of teeth is:

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

Correct Answer: B) Concave mirror

Explanation:

• A) Convex → Diminished images.
• ✅ B) Concave → Enlarged, erect image when object is close.
• C) Plane → Same size, not magnified.
• D) Cylindrical → Not used in dentistry.

Q5. A convex mirror is commonly used as:

A) Dentist’s mirror
B) Car side-view mirror
C) Shaving mirror
D) Torch mirror

Correct Answer: B) Car side-view mirror

Explanation:

• A) Dentist → Concave.
• ✅ B) Convex mirror → Wide field of view, always erect images.
• C, D → Concave mirrors used.

Q6. The radius of curvature of a mirror is:

A) Half the focal length
B) Twice the focal length
C) Equal to focal length
D) Independent of focal length

Correct Answer: B) Twice the focal length

Explanation:

• ✅ B) R = 2f (relation for mirrors).
• A, C, D → Incorrect values.

Q7. A concave mirror forms a real, inverted and same-size image when object is placed at:

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

Correct Answer: C) At centre of curvature

Explanation:

• A) Between F & P → Virtual, erect.
• B) At focus → Image at infinity.
• ✅ C) At C → Real, inverted, same size.
• D) Beyond C → Image between C and F.

Q8. The focal length of a concave mirror is 20 cm. Its radius of curvature is:

A) 10 cm
B) 20 cm
C) 30 cm
D) 40 cm

Correct Answer: D) 40 cm

Explanation:

• ✅ D) R = 2f = 40 cm.
• Others → Wrong values.

Q9. Which mirror always forms a virtual, erect and diminished image?

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

Correct Answer: C) Convex mirror

Explanation:

• A) Concave → Virtual or real depending on object.
• B) Plane → Same size.
• ✅ C) Convex → Always diminished, erect, virtual.
• D) Cylindrical → Not relevant.

Q10. The mirror formula is given by:

A) 1/f = 1/v + 1/u
B) 1/f = 1/u – 1/v
C) v/u = f
D) f = u + v

Correct Answer: A) 1/f = 1/v + 1/u

Explanation:

• ✅ A) Correct mirror formula.
• B, C, D → Incorrect.

Q11. Which lens is used to correct myopia?

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

Correct Answer: B) Concave lens

Explanation:

• ✅ B) Myopia (short-sightedness) → Corrected by diverging concave lens.
• A) Convex → For hypermetropia.
• C, D → Not specific.

Q12. Which lens always forms a virtual, erect and diminished image?

A) Concave lens
B) Convex lens (object near focus)
C) Convex lens (object beyond 2F)
D) None

Correct Answer: A) Concave lens

Explanation:

• ✅ A) Concave lens → Always virtual, erect, diminished.
• B, C → Convex → Depends on object position.
• D → Incorrect.

Q13. The lens formula is:

A) 1/f = 1/v + 1/u
B) 1/f = 1/v – 1/u
C) v/u = f
D) f = u + v

Correct Answer: A) 1/f = 1/v – 1/u

Explanation:

• ✅ A) Lens formula → 1/f = 1/v – 1/u.
• Others → Not correct.

Q14. A ray of light passes through the optical centre of a lens. It:

A) Deviates towards axis
B) Deviates away from axis
C) Emerges undeviated
D) Focuses at focal point

Correct Answer: C) Emerges undeviated

Explanation:

• ✅ C) Through optical centre → Ray goes straight.
• A, B, D → Not correct.

Q15. A concave lens of focal length 15 cm forms an image 10 cm from the lens. The object distance is:

A) 30 cm
B) 20 cm
C) 25 cm
D) 40 cm

Correct Answer: A) 30 cm

Explanation:

• Using 1/f = 1/v – 1/u, f = –15 cm, v = –10 cm.
• 1/–15 = 1/–10 – 1/u → u = –30 cm.
• ✅ A) Object at 30 cm.

Q16. A convex lens of focal length 10 cm is placed. An object is at 20 cm. Image distance will be:

A) 5 cm
B) 10 cm
C) 20 cm
D) 20 cm (real)

Correct Answer: C) 20 cm

Explanation:

• Using 1/f = 1/v – 1/u, f=10, u=–20.
• 1/10 = 1/v + 1/20 → v=20 cm.
• ✅ C) Real, inverted image at 20 cm.

Q17. The power of a lens of focal length 50 cm is:

A) +2 D
B) +4 D
C) +1 D
D) +0.5 D

Correct Answer: C) +2 D

Explanation:

• Power P = 100/f (cm). f=50 cm → 100/50 = 2D.
• ✅ +2 D (convex lens).

Q18. The speed of light is maximum in:

A) Water
B) Glass
C) Air
D) Diamond

Correct Answer: C) Air

Explanation:

• ✅ C) Speed of light decreases with refractive index. Air (n≈1).
• D) Diamond has highest refractive index, lowest speed.

Q19. When a ray of light enters a denser medium obliquely, it:

A) Bends away from normal
B) Bends towards normal
C) Goes undeviated
D) Reflects back

Correct Answer: B) Bends towards normal

Explanation:

• ✅ B) Light slows down in denser medium, bends towards normal.
• A, C, D → Wrong.

Q20. The refractive index of a medium is defined as:

A) Speed of light in vacuum / speed in medium
B) Speed in medium / speed in vacuum
C) Focal length / radius of curvature
D) 1 / focal length

Correct Answer: A) Speed of light in vacuum / speed in medium

Explanation:

• ✅ A) Formula n = c/v.
• B, C, D → Not correct.

Q21. The phenomenon responsible for twinkling of stars is:

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

Correct Answer: B) Refraction

Explanation:

• ✅ B) Due to atmospheric refraction, stars appear to twinkle.
• A, C, D → Not main reasons.

Q22. A ray of light incident normally on a glass slab:

A) Deviates away from normal
B) Deviates towards normal
C) Passes undeviated
D) Totally reflects

Correct Answer: C) Passes undeviated

Explanation:

• ✅ C) At 0° incidence → No bending.
• A, B, D → Not possible.

Q23. The bending of light when it travels from one medium to another is called:

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

Correct Answer: B) Refraction

Explanation:

• ✅ B) Refraction = Bending due to speed change.
• Others → Different phenomena.

Q24. Lateral displacement occurs when light passes through:

A) Plane mirror
B) Concave mirror
C) Glass slab
D) Prism

Correct Answer: C) Glass slab

Explanation:

• ✅ C) Glass slab → Parallel faces cause lateral shift.
• A, B, D → Not correct.

Q25. The phenomenon of rainbow is due to:

A) Reflection only
B) Refraction and dispersion
C) Scattering only
D) Total internal reflection

Correct Answer: B) Refraction and dispersion

Explanation:

• ✅ B) Refraction & dispersion of sunlight through water droplets.
• A, C, D → Partial or not main cause.

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