Science · Textbook solutions

The Human Eye and the Colourful World

Every solved example, exercise, and miscellaneous question, in the order the textbook teaches them. Plus every board question asked from this chapter. · 16 questions

10.2 Defects of Vision and their Correction

4 q

Questions

Practice · 4

IT 10.1 Q1 $What is meant by power of accommodation of the eye?$
IT 10.1 Q2 $A person with a myopic eye cannot see objects beyond 1.2 m distinctly. What should be the type of the corrective lens used to restore proper vision?$
IT 10.1 Q3 $What is the far point and near point of the human eye with normal vision?$
IT 10.1 Q4 $A student has difficulty reading the blackboard while sitting in the last row. What could be the defect the child is suffering from? How can it be corrected?$

Exercises

12 q

Ex 10 Q1 $The human eye can focus on objects at different distances by adjusting the focal length of the eye lens. This is due to$
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Ex 10 Q2 $The human eye forms the image of an object at its$
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Ex 10 Q3 $The least distance of distinct vision for a young adult with normal vision is about$
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Ex 10 Q4 $The change in focal length of an eye lens is caused by the action of the$
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Ex 10 Q5 $-5.5$
Ex 10 Q6 $The far point of a myopic person is 80 cm in front of the eye. What is the nature and power of the lens required to correct the problem?$
Ex 10 Q7 $Make a diagram to show how hypermetropia is corrected. The near point of a hypermetropic eye is 1 m. What is the power of the lens required to correct this defect? Assume that the near point of the normal eye is 25 cm.$
Ex 10 Q8 $Why is a normal eye not able to see clearly the objects placed closer than 25 cm?$
Ex 10 Q9 $What happens to the image distance in the eye when we increase the distance of an object from the eye?$
Ex 10 Q10 $Why do stars twinkle?$
Ex 10 Q11 $Explain why the planets do not twinkle.$
Ex 10 Q12 $Why does the sky appear dark instead of blue to an astronaut?$

What the board has asked from this chapter

Questions per paper · 63 papers · 2023 to 2026

2026

23 q

31 $Observe the given ray diagram showing refraction through a prism and choose the correct option for colour of rays 1 and 2 : Colour of ray 1, Colour of ray 2$
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Dispersion of White Light
31 $Vision defect far-sightedness is found in the eye defects named as :$
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Defects of Vision and their Correction
30 $The pair of eye parts responsible for admitting different amount of light in to the eyes is$
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The Human Eye and Accommodation
31 $To restore clear vision in persons whose size of the eye ball has reduced, he/she is suggested to use suitable$
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Defects of Vision and their Correction
31 $When you look at an object very close to your eyes, the :$
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The Human Eye and Accommodation
34 (a) $What happens when light is scattered from (i) very fine particles and (ii) very large size particles of medium ? Justify your answer in each case.$
Scattering of Light
31 $A thin beam of white light falls on a face of a glass prism and a spectrum is obtained on a screen. Which of the following options is the correct sequence of colours from top to bottom on the screen ?$
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Dispersion of White Light
31 $The vision defect which arises due to gradual weakening of the ciliary muscles and diminishing flexibility of eye lens is :$
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Defects of Vision and their Correction
34 (b) $With the help of a ray diagram, explain any phenomenon of formation of spectrum in nature.$
Dispersion of White Light
For question number 32, two statements are given, one labelled as Assertion (A) and the other is labelled as Reason (R). Select the correct answer to this question from the codes (A), (B), (C) and (D) as given below :
32 $Assertion (A) : When rays of white light pass through a prism, on emerging they give spectrum of seven colours. Reason (R) : It is due to the scattering of light that red light bends minimum and violet light bends the maximum.$
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Dispersion of White Light
35 $Study the given diagram and answer the questions that follow : (a) Write the name of the eye defect shown in the diagram. Where is the image formed in this eye defect with respect to the retina of the eye ? (b) List two causes of this eye defect. (c) With the help of a diagram, show how this eye defect of vision is corrected.$
Defects of Vision and their Correction
34 (A) $(i) How does the change in curvature of the eye lens helps us in the process of seeing the nearby objects clearly ? (ii) State the range of the power of accommodation of a normal human eye.$
The Human Eye and Accommodation
34 (a) $How does the focal length of eye lens change as the distance of the object from the eyes is altered ? Explain.$
The Human Eye and Accommodation
37 $Study the given diagram and answer the questions that follow : (a) Write the name of the eye defect shown in the diagram. Where is the image formed in this eye defect with respect to the retina of the eye ? (b) List two causes of this eye defect. (c) With the help of a ray diagram, show how this defect of vision is corrected.$
Defects of Vision and their Correction
34 (b) $Why is the concave lens used as a corrective lens for a myopic eye ?$
Defects of Vision and their Correction
34 (B) $Draw a ray diagram to show the correction of eye defect of an old man who can not see an object placed closer than 1 m from his eye, clearly.$
Defects of Vision and their Correction
35 $(a) Draw the ray diagram for refraction of light through a glass prism and mark angle of refraction and angle of deviation. (b) When the path of a light ray refracted through a glass prism is reversed how will the angle of deviation change ? Explain.$
Refraction through a Prism
35 $A person is unable to read a book placed closer than 1 meter from his eyes. Identify the defect of vision in his eyes. Draw the ray diagrams to show the defect of vision and its correction.$
Defects of Vision and their Correction
36 $Explain the phenomenon of rainbow formation in the sky. Draw the labelled ray diagram in support of your explanation.$
Dispersion of White Light
36 $What is scattering of light ? How is scattering of light different from reflection of light ? Explain.$
Scattering of Light
37 $(a) What is Tyndall effect ? (b) What happens when sunlight is scattered from the particles of very large size ? (c) ‘Danger’ signals are always red in colour. Why ?$
Scattering of Light
37 $(a) What is hypermetropia ? (b) Write any one cause of hypermetropia. (c) With the help of a suitable ray diagram, explain how hypermetropia is corrected ?$
Defects of Vision and their Correction
37 $A person is suffering from a defect of vision due to the elongation of his/her eye ball. (a) Write the name of the defect of vision and write the other possible cause of this defect of vision. (b) This defect can be corrected by using a suitable lens. Draw the ray diagram for correction of this defect of vision.$
Defects of Vision and their Correction

2025

36 q

12 $When a beam of white light passes through a region of very fine dust particles, the colour of light that scatters the most in that region is :$
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Scattering of Light
12 $Select the correct statement from the following :$
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Scattering of Light
13 $The curvature of eye lens of human eye$
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The Human Eye and Accommodation
13 $In the given figure the angle of incidence and the angle of deviation respectively are :$
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Refraction through a Prism
13 $The white light entering a glass prism, gets split into its constituent colours. It is observed that :$
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Dispersion of White Light
13 $The part of the human eye which can modify the curvature of the eye lens to some extent is :$
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The Human Eye and Accommodation
13 $In the human eye, most of the refraction for the light rays entering the eye occurs at the surface of :$
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The Human Eye and Accommodation
14 $A boy while reading a book, keeps it much beyond 25 cm from his eyes. This defect of vision has arised because of$
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Defects of Vision and their Correction
14 $Most of the refraction for the light rays entering the eye occurs at$
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The Human Eye and Accommodation
14 $The possible way to restore clear vision of those people whose eyeball has elongated is the use of suitable$
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Defects of Vision and their Correction
14 $An old person is suffering from an eye defect caused by weakening of ciliary muscles and diminishing flexibility of the eye lens. If the defect of vision is ‘a’ which can be corrected by lens ‘b’, then ‘a’ and ‘b’ respectively are :$
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Defects of Vision and their Correction
14 $The part of human eye which controls the amount of light entering into it.$
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The Human Eye and Accommodation
15 $The phenomenon responsible for making the smoke particles visible when a beam of sunlight enters a smoke filled room through a narrow hole is :$
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Scattering of Light
15 $Consider the following ray diagram : Here, the angle of incidence and angle of deviation respectively are$
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Refraction through a Prism
Question Nos. 17 to 20 consist of two statements – Assertion (A) and Reason (R). Answer these questions selecting the appropriate option (a), (b), (c) and (d) as given below :
20 $Assertion (A) : White light is dispersed by a glass prism into seven colours. Reason (R) : The red light bends the least while the violet the most when a beam of white light passes through a glass prism.$
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Dispersion of White Light
Question Nos. 17 to 20 consist of two statements – Assertion (A) and Reason (R). Answer these questions selecting the appropriate option (a), (b), (c) and (d) as given below :
20 $Assertion (A) : When ciliary muscles contract, eye lens becomes thin. Reason (R) : Ciliary muscles control the power of the eye lens.$
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The Human Eye and Accommodation
25 (a) $A student has difficulty in reading his textbooks but can read the blackboard clearly while sitting in the last row. Name the defect of vision the student is suffering from. List two reasons due to which this defect arises. Write the nature of the lenses required to correct this defect.$
Defects of Vision and their Correction
25 (A) $Draw a ray diagram to show the refraction of a ray of light passing through an equilateral glass prism. Mark the angle through which the emergent ray bends from the direction of the incident ray and also name it.$
Refraction through a Prism
25 (a) $Give reasons : (i) The sky appears dark to passengers flying at very high altitude. (ii) ‘Danger’ signal lights are red in colour.$
Scattering of Light
25 (B) $Name the type of lenses required by the persons for the correction of their defect of vision called presbyopia. Write the structure of the lenses commonly used for the correction of this defect giving reason for such designs.$
Defects of Vision and their Correction
25 (b) $What is a rainbow ? “We see a rainbow in the sky only after the rainfall.” Why ?$
Dispersion of White Light
25 (b) $Draw a ray diagram to show the path of a ray of light falling obliquely on one of the refracting faces of a triangular glass prism and mark the angle of deviation on it.$
Refraction through a Prism
31 $What is a rainbow ? Draw a labelled diagram to show its formation.$
Dispersion of White Light
31 $A person is suffering from an eye defect in which the far point of the eye is much nearer than infinity. Name the defect of vision the person is suffering from. List two main causes of this defect. Write the type of the corrective lens and draw a ray diagram to show the function of the corrective lens.$
Defects of Vision and their Correction
31 $A person has to keep reading material much beyond 25 cm (say at 50 cm) from the eye for comfortable reading. Name the defect of vision he is suffering from. List two causes responsible for arising of this defect. Draw a labelled diagram showing correction of this defect using eye-glasses. Are these glasses convergent or divergent of light ?$
Defects of Vision and their Correction
32 $+2.0$
Defects of Vision and their Correction
32 $-0.5$
Defects of Vision and their Correction
33 $(a) Draw a diagram to show the dispersion of white light by a glass prism. (b) What is spectrum ? Give reason for its formation.$
Dispersion of White Light
A person allowed a narrow beam of white light from the sun to enter a dark room through a small aperture and placed a glass prism in its path in such a manner that the beam falls on the face AB of the prism as shown in the figure. A screen S is placed on the other side of the prism, facing AC. On turning the prism slowly, a beautiful band of colours is obtained on the screen. It is the spectrum of sunlight.
39 (a) $Name the phenomenon due to which a prism splits the incident white light into a band of colours.$
Dispersion of White Light
The students in a class took a thick sheet of cardboard and made a small hole in its centre. Sunlight was allowed to fall on this small hole and they obtained a narrow beam of white light. A glass prism was taken and this white light was allowed to fall on one of its faces. The prism was turned slowly until the light that comes out of the opposite face of the prism appeared on the nearby screen. They studied this beautiful band of light and concluded that it is a spectrum of white light.
39 (i) $Give any one more instance in which this type of spectrum is observed.$
Dispersion of White Light
A person allowed a narrow beam of white light from the sun to enter a dark room through a small aperture and placed a glass prism in its path in such a manner that the beam falls on the face AB of the prism as shown in the figure. A screen S is placed on the other side of the prism, facing AC. On turning the prism slowly, a beautiful band of colours is obtained on the screen. It is the spectrum of sunlight.
39 (b) $State the reason of getting a band of seven colours in the above case.$
Dispersion of White Light
The students in a class took a thick sheet of cardboard and made a small hole in its centre. Sunlight was allowed to fall on this small hole and they obtained a narrow beam of white light. A glass prism was taken and this white light was allowed to fall on one of its faces. The prism was turned slowly until the light that comes out of the opposite face of the prism appeared on the nearby screen. They studied this beautiful band of light and concluded that it is a spectrum of white light.
39 (ii) $What happens to white light in the above case?$
Dispersion of White Light
A person allowed a narrow beam of white light from the sun to enter a dark room through a small aperture and placed a glass prism in its path in such a manner that the beam falls on the face AB of the prism as shown in the figure. A screen S is placed on the other side of the prism, facing AC. On turning the prism slowly, a beautiful band of colours is obtained on the screen. It is the spectrum of sunlight.
39 (c) (i) $Explain with the help of a labelled ray diagram, an experimental arrangement to show the recombination of the spectrum of white light.$
Dispersion of White Light
The students in a class took a thick sheet of cardboard and made a small hole in its centre. Sunlight was allowed to fall on this small hole and they obtained a narrow beam of white light. A glass prism was taken and this white light was allowed to fall on one of its faces. The prism was turned slowly until the light that comes out of the opposite face of the prism appeared on the nearby screen. They studied this beautiful band of light and concluded that it is a spectrum of white light.
39 (iii) (A) $List two conditions necessary to observe a rainbow.$
Dispersion of White Light
A person allowed a narrow beam of white light from the sun to enter a dark room through a small aperture and placed a glass prism in its path in such a manner that the beam falls on the face AB of the prism as shown in the figure. A screen S is placed on the other side of the prism, facing AC. On turning the prism slowly, a beautiful band of colours is obtained on the screen. It is the spectrum of sunlight.
39 (c) (ii) $Draw a labelled ray diagram to show the formation of a rainbow.$
Dispersion of White Light
The students in a class took a thick sheet of cardboard and made a small hole in its centre. Sunlight was allowed to fall on this small hole and they obtained a narrow beam of white light. A glass prism was taken and this white light was allowed to fall on one of its faces. The prism was turned slowly until the light that comes out of the opposite face of the prism appeared on the nearby screen. They studied this beautiful band of light and concluded that it is a spectrum of white light.
39 (iii) (B) $Draw a ray diagram to show the formation of a rainbow. Mark on it, points (a), (b) and (c) as given below : (a) Where dispersion of light occurs. (b) Where light gets reflected internally. (c) Where final refraction occurs.$
Dispersion of White Light

2024

25 q

12 $When a beam of white light passes through a region having very fine dust particles, the colour of light mainly scattered in that region is :$
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Scattering of Light
12 $The phenomena of light involved in the formation of rainbow are :$
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Dispersion of White Light
13 $The Phenomena of light involved in the formation of a rainbow in the sky are$
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Dispersion of White Light
13 $Consider the following statements in the context of human eye : (a) The diameter of the eye ball is about 2.3 cm. (b) Iris is a dark muscular diaphragm that controls the size of the pupil. (c) Most of the refraction for the light rays entering the eye occurs at the crystalline lens. (d) While focusing on the objects at different distances the distance between the crystalline lens and the retina is adjusted by ciliary muscles. The correct statements are –$
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The Human Eye and Accommodation
13 $The colour of light for which the refractive index of glass is minimum, is :$
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Dispersion of White Light
13 $The lens system of human eye forms an image on a light sensitive screen, which is called as :$
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The Human Eye and Accommodation
14 $In bifocal lenses used for the correction of presbyopia :$
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Defects of Vision and their Correction
Q. Nos. 17 to 20 consists of two statements – Assertion (A) and Reason (R), answer these questions selecting the appropriate option given below :
19 $Assertion (A) : Red light signals are used to stop the vehicles on the road. Reason (R) : Red coloured light is scattered the most so as to be visible from a large distance.$
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Scattering of Light
These questions consist of two statements – Assertion (A) and Reason (R). Answer these questions selecting the appropriate option given below :
19 $Assertion (A) : Myopic eye cannot see distant objects distinctly. Reason (R) : For the correction of myopia converging lenses of appropriate power are prescribed by eye-surgeons.$
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Defects of Vision and their Correction
These questions consist of two statements – Assertion (A) and Reason (R). Answer these questions selecting the appropriate option given below :
19 $Assertion (A) : The colour of clear sky appears blue. Reason (R) : Light of blue colour has longer wavelength as compared to the light of red colour so it is scattered more in the upper atmosphere.$
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Scattering of Light
For Q. Nos. 17 to 20, two statements are given – One labelled as Assertion (A) and the other labelled as Reason (R). Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below :
20 $Assertion (A) : The rainbow is a natural spectrum of sunlight in the sky. Reason (R) : Rainbow is formed in the sky when the sun is overhead and water droplets are also present in air.$
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Dispersion of White Light
24 $When do we say that a particular person is suffering from hypermetropia ? List two causes of this defect. Name the type of lens used to correct this defect.$
Defects of Vision and their Correction
25 (a) $-1$
Defects of Vision and their Correction
25 $-4{\cdot}0$
Defects of Vision and their Correction
25 $What would have been the colour of the sky, if the Earth had no atmosphere ? Give reason to justify your answer.$
Scattering of Light
25 $Name the phenomenon of light responsible for Tyndall effect. Write an event where this phenomenon can be observed.$
Scattering of Light
25 (b) $What is presbyopia ? Name the type of lenses used for the correction of this defect. State the nature (converging/diverging) of the upper part of such lenses.$
Defects of Vision and their Correction
31 (a) $Study the diagram given below and answer the questions that follow : (i) Name the defect of vision depicted in this diagram stating the part of the eye responsible for this condition. (ii) List two causes of this defect. (iii) Name the type of lens used to correct this defect and state its role in this case.$
Defects of Vision and their Correction
31 $Study the diagram given below and answer the questions that follow : (i) Name the defect of vision represented in the diagram. Give reason for your answer. (ii) List two causes of this defect. (iii) With the help of a diagram show how this defect of vision is corrected.$
Defects of Vision and their Correction
31 (b) $What is dispersion of white light ? State its cause. Draw a diagram to show dispersion of a beam of white light by a glass prism.$
Dispersion of White Light
31 (a) $Define the term power of accommodation of human eye. Write the name of the part of eye which plays a major role in the process of accommodation and explain what happens when human eye focuses (i) nearby objects and (ii) distant objects.$
The Human Eye and Accommodation
31 $Define the term power of accommodation of human eye. What happens to the image distance in the eye when we increase the distance of an object from the eye ? Name and explain the role of the part of human eye responsible for it in this case.$
The Human Eye and Accommodation
31 $Name and explain the phenomenon of light due to which the path of a beam of light becomes visible when it enters a smoke filled room through a small hole. Also state the dependence of colour of the light we receive on the size of the particle of the medium through which the beam of light passes.$
Scattering of Light
32 $A narrow beam, PQ of white light is passing through a glass prism ABC as shown in the diagram. Draw a ray diagram to show the emergent beam as it falls on the screen DE. Also write the phenomenon involved and its cause. Using the second law of refraction state which colour of light must have the highest value of refractive index amongst seven visible colours of light. Justify your answer.$
Dispersion of White Light
31 (b) $Draw a ray diagram to show the formation of a rainbow in the sky. On this diagram mark A – where dispersion of light occurs, B – where internal reflection of light occurs and C – where refraction of light occurs. List two necessary conditions to observe a rainbow.$
Dispersion of White Light

2023

23 q

12 $The change in the focal length of an eye lens in human beings is caused by the action of$
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The Human Eye and Accommodation
13 $The phenomena of light involved in the formation of rainbow are$
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Dispersion of White Light
13 $In the following diagram showing dispersion of white light by a glass prism, the colours ‘P’ and ‘Q’ respectively are -$
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Dispersion of White Light
16 $In human eye the part which allows light to enter into the eye is -$
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The Human Eye and Accommodation
For Questions number 17 to 20, two statements are given — one labelled as Assertion (A) and the other labelled as Reason (R). Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below.
19 $Assertion (A) : The angle through which a ray of light bends on passing through a prism is called the angle of deviation. Reason (R) : The peculiar shape of a prism makes the emergent ray bend at an angle to the direction of the incident ray.$
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Refraction through a Prism
For Questions number 17 to 20, two statements are given — one labelled as Assertion (A) and the other labelled as Reason (R). Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below.
19 $Assertion (A) : A person suffering from myopia cannot see the distant objects clearly. Reason (R) : A converging lens is used for the correction of myopic eye as it can form real as well as virtual images of the objects placed in front of it.$
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Defects of Vision and their Correction
24 (a) $When and where does a rainbow appear in the sky ? Draw a labelled ray diagram to show its formation.$
Dispersion of White Light
24 (b) $What is scattering of light ? Why does the clear sky appear blue ?$
Scattering of Light
25 $Observe the following diagram showing an image formation in an eye : (a) Identify the defect of vision shown in the figure. (b) List its two causes and suggest a suitable corrective lens to overcome this defect.$
Defects of Vision and their Correction
25 (a) $A narrow beam XY of white light is passing through a glass prism ABC as shown in the diagram : Trace it on your answer sheet and show the path of the emergent beam as observed on the screen PQ. Name the phenomenon observed and state its cause.$
Dispersion of White Light
25 (A) $Observe the following diagram and answer the questions following it : (i) Identify the defect of vision shown. (ii) List its two causes. (iii) Name the type of lens used for the correction of this defect.$
Defects of Vision and their Correction
25 (b) $It is observed that the power of an eye to see nearby objects as well as far off objects diminishes with age. (i) Give reason for the above statement. (ii) Name the defect that is likely to arise in the eyes in such a condition. (iii) Draw a labelled ray diagram to show the type of corrective lens used for restoring the vision of such an eye.$
Defects of Vision and their Correction
25 (B) $The colour of clear sky from the earth appears blue but from the space it appears black. Why ?$
Scattering of Light
29 $Draw a labelled diagram of a common type of bifocal lens. State the function of each of its parts. Name the defect for the correction of which it is used and state its main cause.$
Defects of Vision and their Correction
29 $List two differences in the characteristic properties of the virtual images formed by the two types of spherical lenses (concave and convex). How are these characteristics of the two lenses used in the correction of the two common defects of vision namely myopia and hypermetropia ?$
Defects of Vision and their Correction
29 $A person is suffering from an eye defect in which the far point of the eye is nearer than infinity. Identify the defect. List two main causes of this defect. Draw a ray diagram to show how this defect is corrected by using a suitable lens.$
Defects of Vision and their Correction
31 $A person is unable to see clearly a poster fixed on a distant wall. He however sees it clearly when standing at a distance of about 2 m from the wall. (a) Draw ray diagram to show the formation of image by his eye lens when he is far away from the wall. (b) List two possible reasons of this defect of vision. (c) Draw ray diagram to show the correction of this defect using appropriate lens.$
Defects of Vision and their Correction
31 $(a) State one important function of the following parts of the human eye : (i) Retina (ii) Pupil (b) State the role of ciliary muscles in focussing objects at varying distances from the eye.$
The Human Eye and Accommodation
31 $Give reasons for the following : (a) Danger signals installed at airports and at the top of tall buildings are of red colour. (b) The sky appears dark to the passengers flying at very high altitudes. (c) The path of a beam of light passing through a colloidal solution is visible.$
Scattering of Light
31 $State reasons for Myopia. With the help of ray diagrams, show the (a) image formation by a myopic eye, and (b) correction of myopia using an appropriate lens.$
Defects of Vision and their Correction
33 $Draw a labelled diagram to show (i) dispersion of a beam of white light, and (ii) formation of a rainbow.$
Dispersion of White Light
33 (A) $Define the term dispersion of white light. State the colour which bends (i) the most, (ii) the least while passing through a glass prism. Draw a diagram to show the dispersion of white light.$
Dispersion of White Light
33 $A person cannot see distinctly the object placed beyond 5 m from his eyes. Name the defect of vision the person is suffering from. Draw a ray diagram to illustrate this defect. List its two possible causes. Name the lens used for the correction of this defect.$
Defects of Vision and their Correction

The 10 board questions to practise first

The questions and kinds of question the board asked most often come first. Each one says how often and when.

Question 1
Asked 4 times: 2023*, 2024*, 2025*, 2026 (* = numbers or wording changed that year) See all 4 times it was asked
36 $Explain the phenomenon of rainbow formation in the sky. Draw the labelled ray diagram in support of your explanation.$
Question 2
This type asked 4 times: 2023, 2024, 2025, 2026. This one: 2026 See all 4 of this type
31 $Vision defect far-sightedness is found in the eye defects named as :$
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Question 3
This type asked 4 times: 2023, 2024, 2025, 2026. This one: 2026 See all 4 of this type
31 $Observe the given ray diagram showing refraction through a prism and choose the correct option for colour of rays 1 and 2 : Colour of ray 1, Colour of ray 2$
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Question 4
This type asked 4 times: 2023, 2024, 2025, 2026. This one: 2026 See all 4 of this type
36 $What is scattering of light ? How is scattering of light different from reflection of light ? Explain.$
Question 5
This type asked 4 times: 2023, 2024, 2025, 2026. This one: 2026 See all 4 of this type
30 $The pair of eye parts responsible for admitting different amount of light in to the eyes is$
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Question 6
Asked 3 times: 2023*, 2025*, 2026 (* = numbers or wording changed that year) See all 3 times it was asked
37 $A person is suffering from a defect of vision due to the elongation of his/her eye ball. (a) Write the name of the defect of vision and write the other possible cause of this defect of vision. (b) This defect can be corrected by using a suitable lens. Draw the ray diagram for correction of this defect of vision.$
Question 7
Asked 3 times: 2024*, 2025*, 2026 (* = numbers or wording changed that year) See all 3 times it was asked
37 $(a) What is hypermetropia ? (b) Write any one cause of hypermetropia. (c) With the help of a suitable ray diagram, explain how hypermetropia is corrected ?$
Question 8
Asked 3 times: 2023*, 2024*, 2026 (* = numbers or wording changed that year) See all 3 times it was asked
34 (A) $(i) How does the change in curvature of the eye lens helps us in the process of seeing the nearby objects clearly ? (ii) State the range of the power of accommodation of a normal human eye.$
Question 9
Asked 3 times: 2023*, 2025*, 2026 (* = numbers or wording changed that year) See all 3 times it was asked
37 $(a) What is Tyndall effect ? (b) What happens when sunlight is scattered from the particles of very large size ? (c) ‘Danger’ signals are always red in colour. Why ?$
Question 10
Asked 3 times: 2023*, 2024*, 2025 (* = numbers or wording changed that year) See all 3 times it was asked
25 (B) $Name the type of lenses required by the persons for the correction of their defect of vision called presbyopia. Write the structure of the lenses commonly used for the correction of this defect giving reason for such designs.$

Quick revision

5 most-asked questions · 12 key points · 3 formulas · 6 diagrams

Checked against NCERT Science (CBSE Class 10), Chapter 10.

Most asked in board papers

1
Defects of vision: myopia, hypermetropia, presbyopia; causes, ray diagrams of the defect and its correction, power of the lens, bi-focal lenses
Asked 4 times: 2026, 2025, 2024, 2023 · 3 marks
2
Prism: refraction and angle of deviation, dispersion of white light, spectrum, which colour bends most, recombination
Asked 4 times: 2026, 2025, 2024, 2023 · 1 mark
3
Human eye: parts and functions (cornea, iris, pupil, ciliary muscles, retina), power of accommodation
Asked 4 times: 2026, 2025, 2024, 2023 · 1 mark
4
Scattering of light: Tyndall effect, why the sky is blue, sky dark at high altitude or with no atmosphere, red danger signals
Asked 4 times: 2026, 2025, 2024, 2023
5
Rainbow: how it forms (refraction, dispersion, internal reflection), labelled ray diagram, conditions to see one
Asked 4 times: 2026, 2025, 2024, 2023 · 2 marks

Must-know points

Parts of the human eye: Light enters through the cornea, where most of the refraction occurs. The iris (dark muscular diaphragm) controls the size of the pupil, which controls the light entering. The crystalline eye lens focuses a real, inverted image on the retina, whose cells send signals by the optic nerve to the brain.
Power of accommodation: The ability of the eye lens to adjust its focal length. Looking at a near object, the ciliary muscles contract, the lens becomes thicker and its focal length decreases. For a distant object they relax, the lens becomes thin and its focal length increases.
Near point and far point: Near point (least distance of distinct vision): the smallest distance at which the eye sees clearly without strain, about 25 cm for a young adult. Far point: the farthest point seen clearly, infinity for a normal eye.
Myopia: Near-sightedness: near objects are clear, distant ones are not; the far point is nearer than infinity and the image forms in front of the retina. Causes: excessive curvature of the eye lens, or elongation of the eyeball. Corrected by a concave lens of suitable power.
Hypermetropia: Far-sightedness: distant objects are clear, near ones are not; the near point is farther than 25 cm and the image forms behind the retina. Causes: the focal length of the eye lens is too long, or the eyeball has become too small. Corrected by a convex lens.
Presbyopia, bi-focal lenses and cataract: Presbyopia: with age the power of accommodation falls as the ciliary muscles weaken and the lens loses flexibility; the near point recedes. Bi-focal lenses: the upper part is concave (distant vision), the lower part convex (reading). Cataract: the lens becomes milky and cloudy; cured by surgery.
Refraction through a prism: A glass prism has two triangular bases and three rectangular faces. A ray bends towards the base at each face, because of the angle between the faces. The angle between the incident ray produced and the emergent ray is the angle of deviation.
Dispersion and spectrum: The splitting of white light into its component colours is dispersion; the coloured band is the spectrum: VIBGYOR. Different colours bend through different angles: red bends the least, violet the most (glass has the lowest refractive index for red).
Recombination: Isaac Newton placed a second, inverted prism after the first: the colours of the spectrum recombined into white light. So sunlight is made of seven colours.
Rainbow: A natural spectrum seen after a rain shower, always opposite to the Sun. Tiny water droplets act like small prisms: they refract and disperse sunlight, reflect it internally, and refract it again as it leaves. Also seen through a waterfall or fountain with the Sun behind you.
Scattering and Tyndall effect: When a beam passes through colloidal particles (smoke, dust, mist), the particles scatter it and the path of the beam becomes visible: the Tyndall effect (sunlight through a dense forest canopy). Very fine particles scatter mainly blue light; larger particles scatter all colours, which looks white.
Blue sky and red signals: Air molecules, smaller than the wavelength of light, scatter blue (shorter wavelength) much more than red, so the sky looks blue. With no atmosphere, or at very high altitude, there is no scattering, so the sky looks dark. Danger signals are red because red is least scattered by fog or smoke, so it is seen far away.

Formulas

Power of a lens

\begin{gathered}P = \frac{1}{f\,(\text{in m})} \\ \text{concave: } P < 0 \\ \text{convex: } P > 0\end{gathered}

Correcting myopia

\begin{gathered}f = -(\text{far point distance}) \\ \text{far point } 80\text{ cm: } f = -0.8\text{ m},\ P = -1.25\text{ D}\end{gathered}

Correcting hypermetropia

\frac{1}{v} - \frac{1}{u} = \frac{1}{f} \quad u = -25\text{ cm},\ v = -(\text{near point}) \quad \text{near point } 1\text{ m: } P = +3\text{ D}

Diagrams to practise

The human eye (Figure 10.1): label cornea · iris and pupil · eye lens and ciliary muscles · retina · optic nerve · aqueous humour
Myopic eye and its correction (Figure 10.2): label far point O′ of the myopic eye · image in front of the retina · concave lens before the eye · image now on the retina
Hypermetropic eye and its correction (Figure 10.3): label near point N′ beyond 25 cm · image behind the retina · convex lens before the eye · object at N (25 cm) imaged on the retina
Refraction through a triangular glass prism (Figure 10.4): label incident ray, angle of incidence · refracted ray, angle of refraction · emergent ray, angle of emergence · angle of prism A, angle of deviation D
Dispersion of white light by a glass prism (Figure 10.5): label beam of white light · glass prism · spectrum on a screen · red at top (least bent), violet at bottom (most bent)
Rainbow formation (Figure 10.8): label sunlight entering a raindrop · refraction and dispersion · internal reflection · refraction out to the observer, Sun behind

Mistakes that cost marks

Swapping the lenses for myopia and hypermetropia

Myopia (cannot see far): concave lens, negative power. Hypermetropia (cannot see near): convex lens, positive power. A lens of -0.5 D means myopia; +2.0 D means hypermetropia.

Ciliary muscles the wrong way round

For a near object the ciliary muscles contract and the lens gets thicker (shorter focal length). For a far object they relax and the lens gets thinner.

Bi-focal halves upside down

Upper part: concave lens, for distant vision. Lower part: convex lens, for reading. So with lenses of -4.0 D and +2.0 D, the -4.0 D one corrects distant vision.

Rainbow without internal reflection

Name all three: refraction (with dispersion) entering the drop, internal reflection, refraction leaving it. The Sun must be behind the observer.

Wrong colour bending most

Violet bends the most and red the least. Red is also scattered the least, which is why danger signals and the rising or setting Sun look red.

10.2 Defects of Vision and their Correction

Questions

Exercises

What the board has asked from this chapter

2026

2025

2024

2023

The 10 board questions to practise first

Question 1

Question 2

Question 3

Question 4

Question 5

Question 6

Question 7

Question 8

Question 9

Question 10

Most asked in board papers

Must-know points

Formulas

Diagrams to practise

Mistakes that cost marks