A person can see objects clearly only upto a maximum distance of $$60\ cm$$. His eye defect, nature of the corrective lens and its focal length are respectively.

Hypermetropia, concave, $$60\ cm$$

MCQ Questions for Class 10 Physics Human Eye And Colorful World Quiz 12

The spread in colours in a rainbow on sky is primarily due to

0%
Dispersion of sunlight
0%
Reflection of sunlight
0%
Refraction of sunlight
0%
Total internal reflection of sunlight

Far point of a person is

5 m

$5 m$ . In order that he has normal vision what kind of spectacles should be use

0%
Concave lens with focal length $5 m$
0%
Concave lens with focal length $10 m$
0%
Convex lens with focal length $5 m$
0%
Convex lens with focal length $-2.5 m$

Explanation

x -

$x-$ distance of far point

= 5 m e t e r s

$=5 meters$

f =

$f=$ focal length of correcting lens

For lens,

v =

$v=$ image distance

= - x

$=-x$ ,

u =

$u=$ object distance

= α

$=\alpha$

\frac{1}{f} = \frac{1}{v} + \frac{1}{u}

$\dfrac{1}{f}=\dfrac{1}{v}+\dfrac{1}{u}$

= \frac{1}{- x} + \frac{1}{α}

$=\dfrac{1}{-x}+\dfrac{1}{\alpha}$

f = - 5 m

$f=-5m$

Since it is negative ,it is concave lens.

When objects at different distances are seen by the eye which of the following remain constant?

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Focal length of eye-lens
0%
Object distance from eye-lens
0%
The radii of curvature of eye-lens
0%
Image distance from eye-lens

Very fine particles mainly scatter _______ coloured light.

0%
Red
0%
Blue
0%
Green
0%
Yellow

The least distance of distinct vision is ________.

0%
25 m
0%
340 cm
0%
25 cm
0%
17 cm

The hypermetropia is a

0%
short sighted defect
0%
long sighted defect
0%
bad vision due to old age
0%
none of these

The defect hypermetropia can be corrected by using a ..................

0%
Convex lens
0%
Concave lens
0%
Concave mirror
0%
Convex mirror

Explanation

The defect hypermetropia can be corrected by using a convex lens of appropriate power.

Hypermetropia is also known as far -sightedness. A person with hypermetropia can see distant objects clearly but cannot see nearby objects distinctly. The near point, for the person, is farther away from the normal near point (

25 c m

$25 cm$ ). Such a person has to keep a reading material much beyond

25 c m

$25 cm$ from the eye for comfortable reading. This is because the light rays from a closeby object are focussed at a point behind the retina (b). This defect arises either because (i) the focal length of the eye lens is too long, or (ii) the eyeball has become too small. This defect can be corrected by using a convex lens of appropriate power. Eye-glasses with converging lenses provide the additional focussing power required for forming the image on the retina.

Choose the correct alternative which matches second and third column .

Column I	Column II	Column III
I. Thickening of eye lens	A. Focal length increases	i. Ciliary muscles contract
II. Thining of eye lens.	B. Focal length decreases	ii. Ciliary muscles elongate

0%
(I)- (B)- (i), (II)-(A)-(ii)
0%
(I)-(B)-(ii), (II)-(A)-(i)
0%
(I)-(A)-(i), (II)-(B)-(ii)
0%
(I)-(A)-(ii), (II)-(B)-(i)

As the thickness of the atmosphere increases the color of scattered light is found in ________ order.

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Blue, violet, yellow, red
0%
Violet, blue, yellow, red
0%
Red, yellow, blue, violet
0%
Violet, blue, red, yellow

Which coloured light scatters least by fog and smoke?

0%
Green
0%
Yellow
0%
Blue
0%
Red

At which place in the eye, image is formed of a person is far-sightedness (hypermetropia)?

0%
On retina
0%
Behind the retina
0%
Infront of retina
0%
On lens of eye

Explanation

Hypermetropia is also known as farsightedness. A person with hypermetropia can see distant objects clearly but cannot see nearby objects distinctly. The near point, for the person, is farther away from the normal near point

(25 c m)

$(25\ cm)$ . This is because the light rays from a closeby object are focussed at a point behind the retina

Which is true for the far sightedness or hypermetorpia from the following?

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Eye lens does not become thin as per requirement
0%
Distant object cannot be seen clearly
0%
Nearby object cannot be seen clearly
0%
Defect can be corrected by using concave lens

Which colour of light is scattered the most (maximum) in the atmosphere?

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Red
0%
Yellow
0%
Blue
0%
Green

The lens used to correct long sightedness or hypermetropla.

0%
Convex lens
0%
Concave lens
0%
Simple lens
0%
Cylindrical lens

What is the least distance of distinct vision of a normal human eye?

0%
10 cm
0%
100 cm
0%
25 cm
0%
25 m

In the dispersion of white light from a prism, the violet light is deviated more than the red light because :

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Velocity of violet rays of light is more
0%
Wavelength of violet rays of light is more
0%
The frequency of violet rays of light is more
0%
The refractive index of prism for violet rays of light is more

How many times do the components of white light undergo deviation while passing through the prism ?

0%
Once
0%
Twice
0%
Thrice
0%
Never

In spectrum obtained with prism which color is deviated maximum ?

0%
Violet
0%
Red
0%
Green
0%
Orange

A person near point of vision is

100 c m

$100 cm$ . Then, the power of lens he must wear so as to have normal vision is :

0%
$-3 D$
0%
$+3 D$
0%
$-1 D$
0%
$+1 D$

Explanation

f = \frac{y D}{y - D} = \frac{100 \times 25}{100 - 25} = \frac{100}{3} c m = \frac{1}{3} m

$f = \dfrac {yD} {y-D} = \dfrac {100 \times 25 }{100 - 25 } = \dfrac {100}{3} cm = \dfrac {1}{3} m$

P = \frac{1}{f} = + 3 D

$P = \dfrac {1}{f} = + 3 D$

Why do we study the Dispersion phenomenon using a glass prism and not a glass slab ?

0%
Light doesn't undergo any deviation inside a glass slab; so cannot be used to study Dispersion
0%
All of the dispersion that takes place at the first interface is exactly reversed at the second parallel surface, 'undoing' the effect of the first interface.
0%
Dispersion occurs only in prism and not in glass slab
0%
None of the above

Dispersion of light is caused due to :

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intensity of light
0%
density of medium
0%
wavelength
0%
none of the above

For the myopic eye, the defect is cured by

0%
Convex lens
0%
Concave lens
0%
Cylindrical lens
0%
Toric lens

Explanation

Myopia is a vision condition, in which a person can see nearby objects clearly but objects farther away appear blurry. Hence the far point of the eye is reduced.

So to cure this , we should use a lens of focal length

f

$f$ such that it forms the image of objects at infinity at the distance of the far point of the person.

Hence, applying the lens' formula

In myopia,

u = \infty, v = - d =

$\displaystyle u=\infty ,v= -d=$ distance of far point
By

\frac{1}{F} = \frac{1}{v} - \frac{1}{u}

$\displaystyle \frac { 1 }{ F } =\frac { 1 }{ v } -\frac { 1 }{ u }$ , we get

f = - d

$\displaystyle f=-d$
Since f is negative, hence the lens used is concave.

A person can see objects clearly only upto a maximum distance of

60 c m

$60\ cm$ . His eye defect, nature of the corrective lens and its focal length are respectively.

0%
Myopia, convex, $60\ cm$
0%
Myopia, concave, $60\ cm$
0%
Hypermetropia, concave, $60\ cm$
0%
Contract, convex, $60\ cm$

Explanation

Range of vision for healthy eye is

25 c m

$25\ cm$ to

\infty

$\infty$ . If the person can see clearly only upto a maximum distance of

60 c m

$60\ cm$ . He is suffering from myopia. A short sighted eye can see only nearer objects. This defect can be removed by using a concave lens of suitable focal length equal to maximum distance seen by person.

f = 60 c m

$f = 60\ cm$ .

A far-sighted person has his near point

50 c m

$50\ cm$ , find the power of lens he should use to see at

25 c m

$25\ cm$ , clearly.

0%
$+1D$
0%
$+2D$
0%
$-2D$
0%
$-1D$

Explanation

Given: A farsighted person has his near point 50cm,

To find the power of lens he should use to see at 25cm, clearly.

Solution:

Distant objects need to be imaged at most 50 cm from the eye.

According to the given criteria,

u = 25 c m, v = - 50 c m

$u=25cm, v=-50cm$

Applying lens formula, we get

$\dfrac 1f=\dfrac 1v+\dfrac 1u\\\implies \dfrac 1f=\dfrac 1{-50}+\dfrac 1{25}\\\implies \dfrac 1f=\dfrac {-1+2}{50}\\\implies f=50cm=0.5m$

The power of the lens he should use is,

$P=\dfrac 1f=\dfrac 1{0.5}=+2D$

To read a poster on a wall, a person with defective vision needs to stand at a distance of

$0.4m$ from the poster. A person with normal vision can read the poster from a distance of

$2.0m$ . Which one of the following lens may be used to correct the defective vision?

0%
A concave lens of $0.5D$
0%
A concave lens of $1.0D$
0%
A concave lens of $2.0D$
0%
A convex lens of $2.0D$

Explanation

From the given problem, it is clear that the person can not see far objects. Therefore, he is suffering from hypermetropia. This defect can be corrected by using a concave lens of suitable power.

$\text{Calculating the power of the concave lens:}$

Given: the object distance

$u=-2m$

the image distance

$v=-0.4m$

Using the lens formula,

$\cfrac { 1 }{ f } =\cfrac { 1 }{ v } -\cfrac { 1 }{ u }$

$P=\cfrac { 1 }{ f } =-\cfrac { 1 }{ 0.4 } -\cfrac { 1 }{ (-2) } =-2$

$P=-2D$
The power of the concave lens should be

$2D$ .

Rainbow is produced when sunlight falls on drops of rain, Which of the following physical phenomena are responsible for this?

0%
Diffusion
0%
Dispersion and total internal reflection
0%
Only refraction
0%
Diffusion, refraction and total internal reflection

If the power of an eye lens increases, then the defect of vision so produced is known as

0%
Colour blindness
0%
Long sightedness
0%
Short sightedness
0%
None of the above

The middle vascular coat that darkens the eye chamber and prevents refraction by absorbing the light rays is

0%
Choroid
0%
Sclera
0%
Retina
0%
Cornea.

A mirage is observed when

0%
Density of air decreases with increase of height
0%
Density of air increases with increase of height
0%
Refractive index of air decreases with increase of height
0%
The Earth acts like a mirror.

Rainbow is produced when sunlight falls on drops of rain. Which of the following physical phenomena is/are responsible for this?

0%
Diffusion
0%
Dispersion and refraction
0%
Only refraction
0%
Refraction, dispersion and total internal reflection.

CBSE Questions for Class 10 Physics Human Eye And Colorful World Quiz 12 - MCQExams.com

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Practice Class 10 Physics Quiz Questions and Answers

CBSE Questions for Class 10 Physics Human Eye And Colorful World Quiz 12 - MCQExams.com

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Practice Class 10 Physics Quiz Questions and Answers

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