Class 10 Physics Chapter 2: Human Eye Questions & Answers
Introduction
The human eye is one of the most fascinating optical instruments created by nature. In Class 10 (CBSE/NCERT) Physics (or Science), the chapter on the human eye (often titled “The Human Eye and the Colourful World”) introduces how light is refracted by the eye, how images are formed, how defects of vision occur and how they are corrected.
Understanding this topic is crucial because many board and competitive exam
questions are drawn from it. This blog covers the key concepts, then presents
questions in board-pattern form: MCQs, very short answer (VSA), short answer,
long answer, some PYQs (Previous Year Questions) and competency questions.
Key Concepts (for reference)
- Structure
of the human eye: cornea, iris, pupil, lens, retina, optic nerve.
- Functioning:
The eye’s lens system focuses light on the retina (which acts like a
screen) to form an image.
- Near
point & far point of human eye (normal vision): near point ≈ 25 cm,
far point = infinity.
- Power
of accommodation: The ability of the eye’s lens to change its focal length
so that objects at different distances can be seen clearly.
- Common
defects of vision: Myopia (short-sightedness), Hypermetropia
(far-sightedness), Presbyopia (age-related) etc., their causes and
corrections by lenses.
- Additional
optics in the chapter (often in the same chapter): Dispersion, scattering
of light, why the sky is blue, why sun appears red at sunrise/sunset.
Questions for Practice:
Here are questions grouped by type, following board-pattern,
with answers.
1. Multiple Choice Questions (MCQs)
Q1. The human eye can focus objects at different
distances by adjusting the focal length of the eye lens. This is due to:
a) Presbyopia
b) Accommodation
c) Near-sightedness
d) Far-sightedness
Right Answer: b) Accommodation
Q2. The human eye forms the image of an object at
its:
a) Cornea
b) Iris
c) Pupil
d) Retina
Right Answer: d) Retina
Q3. The least distance of distinct vision for a young
adult with normal vision is about:
a) 25 m
b) 2.5 cm
c) 25 cm
d) 2.5 m
Right Answer: c) 25 cm
Q4. The change in focal length of an eye lens is
caused by the action of the:
a) Pupil
b) Retina
c) Ciliary muscles
d) Iris
Right Answer: c) Ciliary muscles
Q5. A person cannot see distinct objects beyond 2 m.
The defect can be corrected by using a lens of power:
a) +0.5 D
b) –0.5 D
c) +0.2 D
d) –0.2 D
Right Answer: b) –0.5 D
2. Very Short Answer Questions (10–20 words)
Q1. What is the near point of a normal young adult’s
eye?
Ans: Near point is about 25 cm from the eye.
Q2. Name the transparent front surface of the eyeball
through which light enters.
Ans: Cornea.
Q3. What kind of lens corrects myopia
(short-sightedness)?
Ans: Concave (diverging) lens.
Q4. Why does the pupil appear black?
Ans: Because light enters and is absorbed, not reflected.
Q5. What is the far point of a normal eye?
Ans: Infinity (can see very far objects clearly).
3. Short Answer Questions (≈ 50–70 words)
Q1. Define the power of accommodation of the eye.
Ans: The power of accommodation of the eye is the maximum extent to
which the eye lens can change its focal length to focus near and distant
objects clearly. When ciliary muscles contract or relax, lens curvature changes
and hence focal length changes. This enables the eye to focus objects at
varying distances.
Q2. Explain why stars appear to twinkle.
Ans: Stars appear to twinkle because their light passes through the
Earth’s atmosphere which has varying densities and temperatures. Light rays
undergo continuous refraction (bending) and thus the apparent position and
brightness of stars change rapidly. This effect is less for planets, making
them appear steady.
Q3. How is hypermetropia corrected?
Ans: In hypermetropia (far-sightedness), the image of a nearby object is
formed behind the retina because the eyeball is too short or the lens is too
weak. It is corrected by a convex (converging) lens of appropriate power which
brings the image forward onto the retina, enabling clear vision.
4. Long Answer Questions (≈ 100 words)
Q1. Describe the structure and working of the human
eye.
Ans: The human eye is approximately spherical (diameter ~2.3 cm) and
functions much like a camera. Light enters through the transparent cornea and
pupil (controlled by the iris). Behind the pupil lies a crystalline lens whose
curvature is adjusted by the ciliary muscles to focus light. The refracted rays
fall on the retina, a light-sensitive screen. The retina converts light into
electrical signals sent to the brain via the optic nerve. The eye thus forms a
real inverted image which the brain interprets as upright. Most refraction
occurs at the cornea; the lens provides fine adjustment.
(Also Draw structure of human eye ball)
Q2. What are the common defects of vision and how are
they corrected?
Ans: Common defects include:
- Myopia
(short-sightedness): The eye focuses images of distant objects in
front of the retina, due to elongation of eyeball or excessive curvature.
Corrected with a concave (diverging) lens.
- Hypermetropia
(far-sightedness): The eye focuses images of nearby objects behind the
retina, due to a shortened eyeball or weak lens. Corrected by a convex
(converging) lens.
- Presbyopia:
Age-related reduction in accommodation; corrected by bifocal lenses.
These corrections ensure the image falls on the retina for clear vision.
5. Previous Year Questions (PYQs)
PYQ1 (CBSE): A person has myopia and his far point is
80 cm. What type of lens is required and what is its power?
Soln: Far point = 80 cm = 0.8 m → lens required must form image at
retina for object at infinity. Using lens formula, focal length = –0.8 m →
power P = –1.25 D (concave lens).
PYQ2 (CBSE): Why can a normal eye not see objects
clearly nearer than 25 cm?
Soln: Because the ciliary muscles cannot bulge the lens any more, the
focal length cannot adjust sufficiently to focus very near objects; hence image
forms behind retina and appears blurred.
6. Competency / Higher-Order Thinking Questions
CQ1. A student failing to read the last row of the
classroom blackboard most likely has which vision defect? What lens should be
prescribed and why?
Ans: Difficulty reading distant objects → myopia. Use a concave lens to
diverge incoming rays so that the image forms on the retina.
CQ2. If for a certain eye the near point is 50 cm,
what is the strength (power) of the corrective lens required to enable the
person to read at 25 cm? (Assume normal near point = 25 cm).
Guide for answer: Use lens formula (object u = –25 cm, required image
distance v = –50 cm) and calculate f, then P = 1/f.
Summary
- The
human eye is an optical system that refracts light and focuses it on the
retina.
- Key
parameters: near point ~ 25 cm, far point = infinity for normal eye; power
of accommodation varies.
- Defects:
Myopia, Hypermetropia (and Presbyopia) – each with specific lens
correction.
- Many
board-type questions are asked around these definitions, lens
calculations, and image formation.
- Practice
MCQs, VSAs, short & long answer, PYQs and competency questions to
perform well.
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