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CBSE Questions for Class 10 Physics Human Eye And Colorful World Quiz 9 - MCQExams.com
CBSE
Class 10 Physics
Human Eye And Colorful World
Quiz 9
For a normal eye, the far point is at infinity and the near point of distinct vision is about $$25\ cm$$ in front of the eye. The cornea of the eye provides a converging power of about $$40$$ dioptres, and the least converging power of the eye - lens behind the cornea is about $$20$$ dioptres. From this rough data estimate the range of accommodation (i.e., the range of converging power of the eye-lens) of a normal eye.
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$$10$$ to $$14\ D$$
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$$20$$ to $$24\ D$$
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$$28$$ to $$32\ D$$
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$$14$$ to $$18\ D$$
Explanation
To see object at infinity, eye uses its least converging power.
Power of eye lens, $$P=40+20=60D$$
Power of eye lens is $$1/f\Rightarrow f=5/3 cm$$
To focus on object at the near point, object distance $$u=-d=-25$$ cm
Focal length of eye lens is distance between the cornea and the retina.
Image distance, $$v=5/3\ cm$$
$$\dfrac{1}{v}-\dfrac{1}{u}=\dfrac{1}{f_1}\Rightarrow f_1=16/25cm^{-1}$$
Power is $$100/f_1=64D$$
power of eye lens is $$64-40=24D$$.
The muscles of a normal eye are least strained when the eye is focused on an object .....
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Far away from the eye
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Very close to the eye
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At about $$25$$ cm from the eye
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At about $$1$$ m from the eye
Assertion: Blue colour of sky appears due to scattering of blue colour.
Reason: Blue colour has shortest wave length in visible spectrum.
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both assertion and reason are true and reason is the correct explanation of assertion
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both assertion and reason are true but the reason is not the correct explanation of assertion
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assertion is true but reason is false
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both the assertion and reason are false
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reason is true but assertion is false
Explanation
Blue colour of sky is due to scattering of blue colour to the maximum extent by dust particles. Blue colour appears to be coming from the sky. Blue colour has the least wavelength .
Assertion: The setting sun appears to be red.
Reason: The scattering of light is directly proportional to the wavelength.
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Both assertion and reason are true but the reason is the correct explanation of the assertion
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Both assertion and reason are true but the reason is not the correct explanation of the assertion
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Assertion is true but reason is false
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Both the assertion and reason are false
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Reason is true but assertion is false
Explanation
The setting sun appears to be red because red light which has the greatest wavelength is least scattered and reaches our eyes the most. Other wavelengths are scattered to the longest extent. The scattering of light is inversely proportional to the wavelength. So, the reason given is wrong.
Near point of an eye suffering from long-sightedness is:
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less than 25cm
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greater than 25cm
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equal to 25cm
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infinity
Explanation
In long sightedness, for close objects image is formed behind the retina. This is because the near point of the eye shifts to a distance greater than $$25 \ cm$$ for the eye due to shortening of eyeball.
The sun appears red at the time of sun-rise and sun-set. This is because:
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red colour is least scattered
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red colour is most scattered
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the sun is red in colour
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our eyes can sense only red colour
Explanation
Among the constituent colours of white light, red has the longest wavelength and hence least frequency. Scattering is inversely proportional to wavelength .As a result, red is least scattered among all colours. So, red colour reaches our eyes while all other colours scatter away during sun-rise and sun-set.
Sky appears to be blue in clear atmosphere due to which property of light.
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Scattering
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Polarization
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Diffraction
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Dispersion
Explanation
A clear cloudless daytime sky is blue because molecules in the air scatter blue light from the sun more than they scatter red light. because blue light has a wavelength that is the same size as the particle in the air.
When white light is passed through two consecutive prisms, the resultant will be:
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rainbow colors
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white beam
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no light
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yellow light
Explanation
When white light passes through the first prism, the emergent light disperses into rainbow colours. Then these rays pass through the second prism and combine into white light.
The sky appears blue due to:
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reflection of light
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dispersion and scattering of light
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total internal reflection of light
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blue colour of water droplets
Match the columns:
i.
convex lens
a. presbyopia
ii. concave lens
b. cataract
iii. Artificial lens
c. myopia
iv. focal lens
d. hypermetropia
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i-c,ii-d,iii-a,iv-b
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i-d,ii-c,iii-b,iv-a
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i-b,ii-c,iii-a,iv-d
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i-a,ii-b-iii-d,iv-c
Explanation
Myopia ,near sightedness is corrected by concave lens.
Hypermetropia or, far sightedness is corrected by convex lens.
In cataract natural faulty lens is replaced by artificial lens.
Bi-focal lens is used in presbyopia which generally occurs in old persons.
The refractive defects of the eye can be corrected by _____ :
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Eye glasses
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contact lenses
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Surgical procedures
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All of the above
Explanation
Sometimes, the eye may lose its power of accommodation. In such cases, the vision becomes blurred due to the refractive defects of the eye. These defects can be corrected by the use of suitable spherical lenses
.
It is possible to correct the refractive defects of the eye (such as myopia and hypermetropia) by using contact lenses or by undergoing surgical procedures for example ,surgical treatment of the eye with lasers.
Match the items in list-I with items in list-II and collect the correct answers from the codes given below the lists:
List-I
List-II
I. Myopia
A. Bifocal lens
II. Hyper-metropia
B. Cylindrical lens
III. Presbyopia
C. Concave lens
IV. Astigmation
D. Convex lens
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I-D, II-C, III-A, IV-B
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I-C,11-D,III-A, IV-B
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I-B, II-D, III-A, IV-C
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I-A, II-B, III-C, IV-D
Explanation
Myopia or short sightedness is inability to see distant objects clearly -
It is corrected by Diverging lens (Concave)
Hyper-metropia or long sightedness is inability to see nearby objects clearly- It is corrected by Converging lens (convex)
Presbyopia -Presbyopia is the gradual loss of your eyes' ability (due to aging) to focus on nearby objects- It is corrected by Bifocal lenses
Astigmation -Astigmatism is a type of refractive error in which the eye does not focus light evenly on the retina,It is corrected by - Cylindrical lenses.
thus,
I - C
II - D
III - A
IV - B
Option B is correct.
Sodium lamps are used in foggy conditions because:
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yellow light is scattered less by the fog particles
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yellow light is scattered more by' the fog particles
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yellow light is unaffected during its passage through the fog
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Wavelength of yellow light is the mean of the visible part of the spectrum
Explanation
The higher the wavelength the lesser the scattering. Yellow light has higher wavelength so it is least likely to be scattered among all colours in the visible region (except red & orange). So this light is visible from long distance even when there is foggy weather.
A defect of vision caused due to excessive curvature of the cornea is:
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myopia
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hypermetropia
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astigmatism
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presbyopia
Explanation
Myopia is an eye defect in which one can see objects near to him clearly, but objects farther away are blurry.
Myopia is caused due to excessive curvature of the cornea or more elongation of the eyeball.
A person who is near sighted will have the most trouble reading
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a newspaper in his hands
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a mobile screen in front of him
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a street sign across the street
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the menu in a restaurant
Explanation
A near-sighted person is able to see the near objects clearly but is not able to see the objects which are far from the eyes. In this defect, the image of the far object is formed in front of the retina.
Thus, the person will not have any problem reading a newspaper, watching a mobile screen, or reading the menu card in a restaurant. But the person can not see a street sign clearly as it is located far from him.
If a person can see an object clearly when it is placed at about $$25 cm$$ away from him, he is suffering from:
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astigmatism
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none of these
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myopia
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hypermetropia
Explanation
Minimum distance at which objects can be seen most distinctly is called the least distance of distinct vision or near point of eye. It is $$25cm$$ for a young adult with normal eye.
Long sightedness happens as:
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ciliary muscles tighten
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ciliary muscles weaken
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eyeball size does not change
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all the above happen
Explanation
As we grow old, due to some defect, ciliary muscles become hard and thus can not contract. Thus curvature and focal length of the eye cannot be decreased. So the image is formed behind the retina.
Bi-focal lens is required to correct:
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cataract
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astigmatism
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myopia
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presbyopia
Explanation
Presbyopia is a defect of human eye. With this defect of vision, a person is unable to read or write comfortably. It is corrected by bifocal lens.
A girl viewed an object and found that it is not clearly visible to her. It was found that the image was formed by her eye lens $$3cm$$ away from the pupil of her eyes.The girl can correct this defect by using a:
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concave lens
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convex lens
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bi-focal lens
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plano-convex lens
Explanation
Since the distance between pupil and retina is $$2.3 cm$$ and the image formed is at a distance of $$3 cm$$ from the pupil, it is obvious that the image is formed behind the retina.
This defect is known as hyper-metropia which happens because converging power of eyes lens reduces
So to correct this defect of vision, the girl needs to use a convex lens. It will form the image at the retina by increasing the combined power.
What is the black circular aperture in our eyes and why does it appear black?
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The aperture is known as iris and it appears black as no light is reflected from it.
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The aperture is known as the pupil and it appears black as all light is reflected from it.
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The aperture is known as iris and it appears black as all light is reflected from it.
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The aperture is known as the pupil and it appears black as no light is reflected from it.
Explanation
A small aperture is present at the center of the iris. The size of the aperture is variable and self-adjustable. This aperture is known as the pupil. The pupil appears black as no light is reflected from it.
Which of the following is not true for the eye lens?
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It is composed of a fibrous, jelly-like material.
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Its curvature can be modified to some extent by the ciliary muscles.
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When the muscles are relaxed, the lens becomes thin.
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When the muscles are relaxed, the lens becomes thick.
Explanation
The eye lens is composed of fibrous, jelly-like material. Its curvature can be modified to some extent by the ciliary muscles. The change in the curvature of the eye lens can thus change its focal length. When the muscles are relaxed, the lens becomes thin. Thus option $$D$$ is incorrect.
Match the columns
i. amount of light entering into eye controlled by
a. rodes
ii.
colour sensing cells
b. cones
iii.cells helping in vision in dim light
c. iris
iv.
junction of optic nerve and retina
d. blindspot
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i-a,ii-b,iii-c,iv-d
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i-d,ii-c,iii-b-iv-a
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i-c,ii-b,iii-a,iv-d
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i-b,ii-a,iii-c,iv-b
Explanation
Iris controls the amount of light entering the eye.
Cones are colour sensing cells.
Rode cells help in vision in dim light.
At the junction of optic nerve and retina there are no rodes and cones.No image is formed at this point as it is insensitive to light.This point is called blind spot.
Fill up the blanks:
a) light sensitive screen of human eye..............
b) near sightedness is corrected by..................
c) hypermetropia is corrected by.................
d) range of vision for a normal eye............
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a. retina
b. concave lens
c. convex lens
d. $$25cm-$$infinity
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a. cornea
b. convex lens
c. concave lens
d. $$0-25cm$$
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a. iris
b. converging lens
c. diverging lens
d. $$0-$$infinity
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a. sclera
b. diverging lens
c convex lens
d. infinity
Explanation
The screen of eye is called the retina.It is a delicate membrane having enormous number of light sensitive cells or photo-receptors.
Myopia or, near sightedness is corrected by concave lens.
Hypermetropia or, far sightedness is corrected by convex lens.
Range of vision for normal eye is $$25cm$$ to infinity.
Which colour of light is scattered by very large particles?
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Blue
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Violet
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Indigo
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White
Explanation
Scattering of light is the phenomenon in which light rays get deviated from their straight path on striking an obstacle like dust or gas molecules, water vapors, etc. Fine particles scatter light of shorter wavelength and larger particles scatter light of longer wavelength. However, if the size of the scattering particles is large enough, then, the scattered light may even appear white.
Fill in the blanks:
For a human eye lens, for n
earby objects, focal length ____ while for far away objects focal length ____ .
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remains the same, decreases
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increases, decreases
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decreases, increases
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increases, remains the same
Explanation
The curvature of the eye lens can be modified to change its focal length to some extent by the ciliary muscles. When the ciliary muscles contract, the focal length of the eye decreases enabling us to see nearby objects clearly. Similarly, when the muscles are relaxed, the focal length increases. This enables us to see distant objects clearly.
Match the following
List I
List II
1
Adjustment of focal length
a
Accommodation
2
Least distance of distinct vision
b
Infinity
3
Farthest point of visibility
c
25 cm
4
Vision impairment
d
Cataract
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1-b, 2-c, 3-a, 4-d
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1-d, 2-c, 3-b, 4-a
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1-a, 2-c, 3-b, 4-d
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1-c, 2-a, 3-d, 4-b
Explanation
The change in the curvature of the eye lens can change its focal length to facilitate clear vision of close or far away objects. The ability of the eye lens to adjust its focal length is called accommodation. The least distance of distinct vision for a young adult with normal vision is about 25 cm. The farthest point up to which the normal eye can see objects clearly is infinity.
A cataract is a vision impairment which involves clouding of the normally clear lens of your eye. For people who have cataracts, seeing through cloudy lenses is a bit like looking through a frosty or fogged-up window.
Match the following
List I
List II
1
Change in curvature
a
25 cm
2
Relaxed ciliary muscles
b
Curvature of the lens decreases
3
Thick lens
c
Change in focal length
4
Near point
d
Focal length increases
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1-b, 2-c, 3-a, 4-d
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1-c, 2-d, 3-b, 4-a
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1-a, 2-c, 3-b, 4-d
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1-c, 2-a, 3-d, 4-b
Explanation
The change in the curvature of the eye lens can thus change its focal length to facilitate clear vision of close or far away objects. The ability of the eye lens to adjust its focal length is called accommodation. When the muscles are relaxed, the curvature decreases making the lens thin and the focal length increases. Similarly when the ciliary muscles contract the curvature of the eye lens decreases making them thicker, this decreases the focal length of the eye. For a young adult with normal vision, the near point is about 25 cm
The minimum distance at which objects can be seen without any strain is
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$$25\ cm$$
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Near point
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Least distance of distinct vision
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All of the above
Explanation
To see an object comfortably and distinctly, it must be held at about $$25\ cm$$ from the eyes. The minimum distance, at which objects can be seen most distinctly without strain, is called the least distance of distinct vision or near point of the eye. For a young adult with normal vision, the near point is about $$25\ cm.$$
The refractive defects of vision are
a. Myopia b. Cataract
c. Hypermetropia d. Presbyopia
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a and b
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a, c and d
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b and c
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All of the above
Explanation
Sometimes, the eye may lose its power of accommodation. In such cases, the vision becomes blurred due to the refractive defects of the eye. Three common refractive defects of vision are myopia or near-sightedness, Hypermetropia or farsightedness and Presbyopia.
A cataract is a clouding of eye lenses. it is denser so eyes make blurred images on the retina.
Myopia can be corrected by using a _____.
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Converging lens
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Bifocal lens
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Diverging lens
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None of the above
Explanation
In a myopic eye, the image of a distant object is formed in front of the retina and not at the retina itself. This defect can be corrected with the help of a concave or diverging lens of suitable power as it will bring the image back on the retina.
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