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Class 10 Science Chapter 10: The Human Eye and the Colourful World MCQs with answers

10 multiple-choice questions on The Human Eye and the Colourful World, each with its answer and the reason, written from the NCERT chapter. Open a question's solution to check your working; then take the free test to find your next chapter.

Question 1
The part of the human eye that controls the size of the pupil is the
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Answer: (b) iris

The iris is a dark muscular diaphragm that controls the size of the pupil; the ciliary muscles change the curvature of the lens, not the pupil.

Question 2
Most of the refraction of light entering the human eye takes place at the
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Answer: (b) outer surface of the cornea

Most refraction occurs at the outer surface of the cornea; the eye lens only provides the finer adjustment of focal length.

Question 3
The image that the eye lens forms on the retina is
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Answer: (b) real and inverted

The eye lens forms an inverted, real image of the object on the retina.

Question 4
Rohan looks up from his book at a hill far away. To see the hill clearly, his ciliary muscles
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Answer: (a) relax, the lens becomes thinner and its focal length increases

For a distant object the ciliary muscles relax, the lens becomes thin and its focal length increases. Option (b) is the state for a near object; (c) pairs a thicker lens with a longer focal length; (d) pairs contracted muscles with a thinner lens.

Question 5
Anjali watches a kite as it drifts farther away from her. Her eye keeps the kite's image sharp on the retina by
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Answer: (d) increasing the focal length of the eye lens

The retina stays a fixed distance from the eye lens, so the eye cannot move either of them; as the kite recedes the ciliary muscles relax, the lens becomes thinner and its focal length increases. The pupil only controls how much light enters.

Question 6
Which of these can a young adult with normal vision not see distinctly?
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Answer: (d) a coin held 10 cm from the eye

A normal eye sees clearly from its near point, about 25 cm, out to infinity. The coin at 10 cm is nearer than the near point; the page, the bus and the Moon all lie within the range.

Question 7
The crystalline lens of an elderly man's eye has turned milky and cloudy. The condition, and how it is treated, is
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Answer: (b) cataract, treated by surgery

A milky, cloudy lens in old age is cataract. It is not a refractive defect, so it is treated by cataract surgery, not by spectacles.

Question 8
In a myopic eye, the image of a distant object is formed
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Answer: (c) in front of the retina

In myopia the image of a distant object forms in front of the retina, not on it. Behind the retina is the case of hypermetropia for a near object.

Question 9
Which one of the following can cause myopia?
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Answer: (c) elongation of the eyeball

Myopia arises from excessive curvature of the eye lens or elongation of the eyeball. A small eyeball and a long focal length cause hypermetropia; a cloudy lens is cataract.

Question 10
In a hypermetropic eye, light from a nearby object is focussed behind the retina. One reason for this is that the
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Answer: (c) eyeball has become too small

Hypermetropia arises when the focal length of the eye lens is too long or the eyeball has become too small. Excess curvature and an elongated eyeball cause myopia.

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