📘 Human Eye and Colourful World – MCQs (Class 10 Science)

🔹 Part 3: Questions 51–75

Q51. The lens used in the human eye is:

A) Plano-concave
B) Concave
C) Convex
D) Cylindrical

Correct Answer: C) Convex

Explanation:

• A) Plano-concave → Diverging lens.
• B) Concave → Cannot form real images.
• ✅ C) Human eye → Biconvex lens for real image on retina.
• D) Cylindrical → Corrects astigmatism, not natural lens.

Q52. The retina contains two types of cells called:

A) Cones and rods
B) Ciliary and iris
C) Optic and corneal
D) Aqueous and vitreous

Correct Answer: A) Cones and rods

Explanation:

• ✅ A) Rods → Dim light, Cones → Colour vision.
• B, C, D → Wrong parts.

Q53. Which part of the eye regulates the amount of light entering?

A) Cornea
B) Pupil
C) Lens
D) Retina

Correct Answer: B) Pupil

Explanation:

• A) Cornea → Refraction.
• ✅ B) Pupil → Controls light entry (adjusted by iris).
• C) Lens → Focuses light.
• D) Retina → Detects light.

Q54. Which part of the human eye is light-sensitive?

A) Lens
B) Retina
C) Pupil
D) Iris

Correct Answer: B) Retina

Explanation:

• ✅ B) Retina → Has rod & cone cells, responds to light.

Q55. The focal length of the eye lens decreases when:

A) Ciliary muscles contract
B) Ciliary muscles relax
C) Cornea thickens
D) Iris expands

Correct Answer: A) Ciliary muscles contract

Explanation:

• ✅ A) Contraction increases curvature, decreases focal length → For near vision.

Q56. The defect of vision in which parallel rays focus in front of retina is:

A) Hypermetropia
B) Myopia
C) Presbyopia
D) Astigmatism

Correct Answer: B) Myopia

Explanation:

• ✅ B) Myopia → Image before retina → Concave lens corrects.

Q57. Which defect occurs due to loss of accommodation power of the eye with ageing?

A) Myopia
B) Hypermetropia
C) Presbyopia
D) Astigmatism

Correct Answer: C) Presbyopia

Explanation:

• ✅ C) Ageing reduces lens flexibility.

Q58. The splitting of sunlight by raindrops into seven colours is due to:

A) Refraction and dispersion
B) Only reflection
C) Scattering
D) Polarisation

Correct Answer: A) Refraction and dispersion

Explanation:

• ✅ A) Refraction + dispersion inside drops → Rainbow.

Q59. The scattering of light depends on:

A) Angle of incidence
B) Wavelength of light
C) Shape of source
D) Distance from source

Correct Answer: B) Wavelength of light

Explanation:

• ✅ B) ∝ 1/λ⁴ → Shorter wavelengths scatter more.

Q60. The stars appear to twinkle while planets do not because:

A) Planets are closer, appear as extended sources
B) Stars are brighter
C) Planets emit no light
D) Planets are smaller

Correct Answer: A) Planets are closer, appear as extended sources

Explanation:

• ✅ A) Extended source averages out refraction variations.

Q61. The sun appears reddish at sunrise and sunset due to:

A) Dispersion
B) Reflection
C) Scattering of shorter wavelengths away
D) Refraction

Correct Answer: C) Scattering of shorter wavelengths away

Explanation:

• ✅ C) Blue scattered → Red passes.

Q62. The time difference between actual sunset and apparent sunset is about:

A) 2 minutes
B) 4 minutes
C) 6 minutes
D) 8 minutes

Correct Answer: B) 4 minutes

Explanation:

• ✅ B) 2 min earlier sunrise + 2 min delayed sunset = 4 min total.

Q63. The splitting of light into colours by a prism occurs because:

A) Refractive index same for all colours
B) Refractive index different for different colours
C) Reflection is maximum
D) Lens formula

Correct Answer: B) Refractive index different for different colours

Explanation:

• ✅ B) Violet deviates more, red least.

Q64. Which part of the eye provides most of the refraction of light?

A) Cornea
B) Lens
C) Retina
D) Iris

Correct Answer: A) Cornea

Explanation:

• ✅ A) Cornea provides ~2/3 of refraction, lens fine-tunes.

Q65. Which phenomenon causes the sky to appear blue?

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

Correct Answer: B) Scattering

Explanation:

• ✅ B) Rayleigh scattering → Shorter wavelengths scatter more.

Q66. A person with myopia can see:

A) Distant objects clearly only
B) Nearby objects clearly only
C) Both near and far clearly
D) Nothing clearly

Correct Answer: B) Nearby objects clearly only

Explanation:

• ✅ B) Myopia = Short-sightedness.

Q67. Which of the following lenses is used to correct hypermetropia?

A) Concave lens
B) Convex lens
C) Cylindrical lens
D) Bifocal lens

Correct Answer: B) Convex lens

Explanation:

• ✅ B) Convex → Converging lens shifts near images to retina.

Q68. The part of the eye where image is formed is:

A) Cornea
B) Lens
C) Retina
D) Iris

Correct Answer: C) Retina

Explanation:

• ✅ C) Retina → Light-sensitive screen of the eye.

Q69. Which phenomenon is responsible for stars appearing higher than actual?

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

Correct Answer: B) Refraction of starlight

Explanation:

• ✅ B) Atmospheric refraction shifts apparent position upward.

Q70. The colour of danger signals is red because:

A) Red is attractive
B) Red scatters least and is visible from far
C) Red absorbs most light
D) Red travels slowest

Correct Answer: B) Red scatters least and is visible from far

Explanation:

• ✅ B) Long wavelength → Least scattered → Visible far away.

Q71. The scattering of light by particles smaller than wavelength of light is called:

A) Rayleigh scattering
B) Mie scattering
C) Dispersion
D) Diffraction

Correct Answer: A) Rayleigh scattering

Explanation:

• ✅ A) Rayleigh → Explains blue sky, red sunset.

Q72. The eye defect corrected by cylindrical lens is:

A) Myopia
B) Hypermetropia
C) Presbyopia
D) Astigmatism

Correct Answer: D) Astigmatism

Explanation:

• ✅ D) Astigmatism due to uneven curvature of cornea → Cylindrical lens corrects.

Q73. The part of the eye where optic nerve leaves has no vision because:

A) Lens absent there
B) No cornea present
C) No rods and cones
D) Pupil closed

Correct Answer: C) No rods and cones

Explanation:

• ✅ C) Blind spot → No sensory cells.

Q74. The actual cause of rainbow is:

A) Reflection from sun
B) Dispersion, refraction and internal reflection by raindrops
C) Absorption by clouds
D) Interference

Correct Answer: B) Dispersion, refraction and internal reflection by raindrops

Explanation:

• ✅ B) All three processes occur inside raindrops.

Q75. The defect of eye where distant objects are seen clearly but near objects are blurred is:

A) Myopia
B) Hypermetropia
C) Presbyopia
D) Astigmatism

Correct Answer: B) Hypermetropia

Explanation:

• ✅ B) Hypermetropia (farsightedness) → Near vision defective.

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