Human Eye and Colourful World Class 10 Important Questions with Answers | CBSE Science Chapter 11 (2024-25)

The following is a list of all the important topics that are covered under the chapter on Human Eye and Colourful World:

1. Introduction to The Human Eye and Colourful World

2. Structure of a Human Eye

3. Defects of a Human Eye

4. Dispersion of White Light by a Glass Prism

5. Atmospheric Refraction

6. Twinkling of Stars

7. Scattering of Light

Study Important Questions for Class 10 Science Chapter 11 - Human Eye and Colourful World

Very Short Answer Questions (1 Mark)

1. When a person is myopic, he/ she can clearly see

1. Both nearby and far-off objects

2. Only nearby objects

3. Only far-off objects

4. Neither near nor far off objects

Ans: b. Only nearby objects

2. The defect of myopia can be corrected by using

1. Concave lens

2. Convex lens

3. Either concave or convex

4. A complicated combination of lenses.

Ans: a. Concave lens

3. The colour that is scattered the least by the tiny particles and the atoms/ molecules of the atmosphere is

1. Violet

2.  Green

3.  Yellow

4.  Red

Ans. d. Red

4. Which of the following phenomena contributes significantly to the reddish appearance of the sun at sunrise or sunset?

1. Dispersion of light

2. Scattering of light

3. Total internal Reflection

4. Reflection of light from the earth

Ans: b. Scattering of light

5. The focal length of the eye lens increases when eye muscles.

1. are relaxed and lens becomes thinner

2. contract and lens becomes thicker

3. are relaxed and lens becomes thicker

4. Contract and lens become thinner.

Ans: a. are relaxed and lens becomes thinner

6. Define the power of accommodation?

Ans: The power of the eye lens to focus on objects near or far from the retina by adjusting its focal length is called the power of accommodation.

7. Which part of the human eye provides most of the refraction for the light rays entering the eye?

Ans: Cornea and Aqueous humour provides most of the refraction for the light rays entering the eye.

8. What happens to the image distance in the eye when we increase the distance of an object from the eye?

Ans: When the distance of an object from the eye is increased, the image distance remains the same and the image is formed on the retina of the eye.

9. What happens to the pupil of the eye when the light is very bright?

Ans: When the light is very bright, the pupil’s size becomes smaller and limits the extent of light entering the eye.

10. Which part of the human eye conveys the electrical signals generated by the light sensitive cells of the retina to the brain?

Ans: Optic nerves convey the electrical signals generated by the light sensitive cells of the retina to the brain.

11. The human eye can focus on objects at different distances by adjusting the focal length of the eye lens. This is due to

1. Presbyopia

2. Accommodation

3. Near-sightedness

4. Far-sightedness

Ans: b. Accommodation

12. The human eye forms the image of an object at its

1. Cornea

2. Iris

3. Pupil

4. Retina

Ans: d. Retina

13. The least distance of distinct vision for an eye lens is caused by the action of the

1. $25$ m

2. $2.5$ cm

3. $25$ cm

4. $2.5$ m

Ans: c. $25$ cm

14. The change in focal length of an eye lens is caused by the action of the

1. Pupil

2. Retina

3. Ciliary muscles

4. Iris

Ans: c. Ciliary muscles

15. What would have been the colour of the sky if there had not been any atmosphere around the earth?

Ans: The colour of the sky would be black if there had not been any atmosphere around the earth.

16. For dispersion of light through a prism which colour has a maximum deviation?

Ans: Violet has the maximum deviation for dispersion of light through a prism. 

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

Ans: The least distance of distinct vision of a normal human eye is $25$ cm.

18. Name the muscle responsible for bringing change in the focal length of the eye lens?

Ans: Ciliary muscles are responsible for bringing change in the focal length of the eye lens. 

19. Name one defect of vision which cannot be corrected by any type of spectacle lens?

Ans: Cataract, clouding of the lens of the eyes is a vision defect that cannot be corrected by any type of spectacle lens.

20. State one effect produced by the scattering of light by the atmosphere?

Ans: Tyndall effect is produced by the scattering of light by the atmosphere.

21. What is the nature of the image formed on the retina of the eye?

Ans: The image formed on the retina of the eye is real and inverted.

22. What type of lens is used for correcting hypermetropia?

Ans: Convex lens is used to rectify hypermetropia or long-sightedness.

23. Who was the first person to obtain the spectrum of sunlight?

Ans: Sir Isaac Newton was the first person to obtain the spectrum of sunlight.

24. As light rays pass from air into glass prisms, are they refracted towards or away from the normal?

Ans: As light rays pass from air into a glass prism they are refracted towards the normal as glass is denser than air.

25. Which colour has the largest wavelength?

Ans: Red colour of light has the longest wavelength in the visible spectrum of light.

26. Which defect of vision can be rectified using a concave lens?

Ans: Myopia (short-sightedness) can be rectified using a concave lens.

27. What phenomenon causes the twinkling of stars on a clear night?

Ans: Atmospheric refraction is the phenomenon that causes the twinkling of stars on a clear night.

28. What is meant by scattering of light?

Ans: Scattering of light is defined as the change in the direction of light on striking an obstacle such as dust, water vapour, etc.

Short Answer Questions (2 Marks)

1. 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?

Ans: The far point of a myopic person is given as $80$ cm. 

Since the person is Myopic, the lens would be concave and the focal length will be negative.

$\Rightarrow f=-80\text{ }cm=-0.8\text{ }m$

We know, the power of a lens is equal to the reciprocal of the focal length.

$\Rightarrow P=\dfrac{1}{f}$

$\Rightarrow P=\dfrac{1}{-0.8}=-1.25D$

The nature of the lens is concave and its power is $-1.25D$.

2. Draw a diagram to show the dispersion of white light by a glass prism.

Ans: Diagram depicting the dispersion of white light by a glass prism is drawn below.

3. Name the phenomenon responsible for the observed twinkling of stars. Will this twinkling be observed by an observer on the moon?

Ans: The phenomenon responsible for the twinkling of stars is atmospheric refraction.

Since the moon has no atmosphere, the observer on the moon will not be able to observe the twinkling of stars.

4. Name the part of the eye that

1. determines the colour of a person’s eye

Ans: Iris

2. Controls the amount of light entering the eye

Ans: Iris

5. What is the role of the ciliary muscles?

Ans: The main role of the ciliary muscles is to hold the eye lens in its position. The ciliary muscles contract and relax to focus on near or far away objects by changing the shape of the eye lens which in turn increases or decreases the focal length of the eye lens.

6. Why is a convex lens called a converging lens?

Ans: A convex lens focuses all the parallel light rays at its focus after refraction. Hence, it is called a converging lens.

7. State the role of the eye lenses in the human eye?

Ans: The eye lens focuses the light rays entering the eye on the retina forming a real and an inverted image of the object on the retina.

8. A person with a myopic eye cannot see objects beyond $1.2$ m distinctly. What should be the corrective lens used to restore proper vision?

Ans: Since the person is myopic and cannot see objects clearly beyond $1.2$ m, he should use a concave lens having a focal length $1.2$ m to restore his normal vision.

9. What is the far point and near the point of the human eye with normal vision?

Ans: For a human eye with proper vision, the near point is $25$ cm from the eye and the far point is at infinity.

10. 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?

Ans: Since, the student has difficulty reading the blackboard, sitting in the last row, he is suffering from myopia or short-sightedness. A concave lens of suitable power should be used to correct his vision defect.

11. Why is a normal eye not able to see clearly the objects placed closer than 25 cm?

Ans: The normal eye is unable to see the objects clearly placed closer than $25$ cm because at a distance of $25$ cm power of accommodation gets exhausted. Hence, the eye is unable to focus the light rays on the retina, when the object is placed closer than $25$ cm. 

12. Why does the Sun appear reddish early in the morning?

Ans: During sunrise, the sun is at the farthest distance from the earth’s surface. The light rays travel a large distance in the Earth’s atmosphere before reaching our eyes. 

While passing through the atmosphere, the light rays with shorter wavelengths get scattered by the Earth’s atmosphere and the red-colored light with the longest wavelength is able to reach our eyes. Hence, the Sun appears reddish early in the morning. 

13. A person wears eyeglass of focal length $70$ cm. What is the far point of the person?

Ans: The focal length of the eye glass is given as,

$\Rightarrow f=-70$ cm

$\Rightarrow u=-\infty $

From the lens formula, we have: 

$\Rightarrow \dfrac{1}{f}=\dfrac{1}{v}-\dfrac{1}{u}$

$\Rightarrow \dfrac{1}{-70}=\dfrac{1}{v}-\dfrac{1}{-\infty }$

$\Rightarrow \dfrac{1}{-70}=\dfrac{1}{v}$

$\Rightarrow v=-70$ cm

Hence, the far point of the person will be $70$ cm.

14. If your eyeglasses have a focal length $60$ cm what is your near point?

Ans: The focal length of the eye glass is given as,

$\Rightarrow f=60$ cm

$\Rightarrow u=-25$ cm

From the lens formula, we have: 

$\Rightarrow \dfrac{1}{f}=\dfrac{1}{v}-\dfrac{1}{u}$

$\Rightarrow \dfrac{1}{60}=\dfrac{1}{v}-\dfrac{1}{-25}$

$\Rightarrow \dfrac{1}{60}-\dfrac{1}{25}=\dfrac{1}{v}$

$\Rightarrow v=-43$ cm

Hence, the near point will be $43$ cm.

15. Why do we observe random wavering or flicking of the objects near a fire or on a very hot day?

Ans: We observe random wavering or flicking of the objects near a fire or on a very hot day because of atmospheric refraction. The area above the fire is hot and is lighter than the cool air above it due to which its refractive index is low and density also does not remain the same. Therefore, the apparent position of the object flickers.

16. Why are we not able to see things clearly when we come out of a dark room?

Ans: In a dark room, the iris expands the pupil which allows more light to enter the eye. As we come out of the darkroom, a large amount of light enters our eyes and because of the glare, we are not able to see things clearly.

17. What is the function of the optic nerve in the human eye?

Ans: Optic nerve carries the visual information from the retina to the brain in the form of electrical signals.

18. Why do different colours deviate through different angles on passing through a prism?

Ans: Different colours deviate through different angles on passing through a prism because different colours with different wavelengths travel through glass at different speeds and the glass has a different refractive index for different colours.

19. Name the defect of vision in the person

a. Whose near point is more than $25$ cm away?

Ans: Hypermetropia

b. Whose far point is less than infinity.

Ans: Myopia

20. What is a spectrum?

Ans: A continuum of colour obtained by dispersion of white light by passing through a prism is called a spectrum.

21. Why does the clear sky look blue?

Ans: As white light passes through the atmosphere, the tiny particles held in the atmosphere scatter the light of a shorter wavelength. Therefore, blue light having the shortest wavelength is scattered the most and the clear sky appears blue.

22. Can visible light be scattered by atoms/molecules in the earth’s atmosphere?

Ans: Yes, visible light is scattered by atoms/molecules in the earth’s atmosphere as the size of molecules/atoms is much less than the wavelength of visible light.

23. Why does the sky appear dark instead of blue to an astronaut?

Ans: Outer space does not have an atmosphere. As a result, the light does not scatter into its constituent colours in outer space and hence the sky appears dark instead of blue to an astronaut.

24. What is the basic cause of atmospheric refraction?

Ans: Atmospheric refraction is caused by the bending of light when it passes through the layers of the Earth’s atmosphere with different optical densities.

25. What is the range of vision?

Ans: The range of vision of a normal human eye is the distance between the near point and far point of the human eye. Hence, for a normal human eye, it ranges from $25$ cm to infinity.

Short Answer Questions (3 Marks)

1. Explain in brief:

a. What is hypermetropia?

Ans: Hypermetropia (long-sightedness) is a vision defect where nearby objects appear blurred but the distant objects can be seen clearly.

b. What are the two causes of this defect of vision?

Ans: The two possible causes of this defect are:

(i). An increase is the focal length of the eye lens or the power of the eye lens decreases 

(ii). Size of the eyeball decreases

2. Explain the scattering of light?

Ans: Scattering of light is defined as the change in the direction of light on striking an obstacle such as dust, water vapour, etc.

3. A person is known to use a lens of power

1. $-5.5$ D for his distant vision

2. $+1.5$ D for his near vision

Calculate the focal length of the lens used for correcting his

1. Distant vision 

Ans: For distant vision, the power of lens is given to be $-5.5$ D.

The focal length is given by,

$\Rightarrow f=\dfrac{1}{P}$

$\Rightarrow f=\dfrac{1}{-5.5}$  m

$\Rightarrow f=-18.2$ cm

2. Near vision problems.

Ans: For near vision, the power of the lens is given to be $+1.5$ D.

The focal length is given by,

$\Rightarrow f=\dfrac{1}{P}$

$\Rightarrow f=\dfrac{1}{1.5}$  m

$\Rightarrow f=66.7$ cm

4. What is presbyopia? State the causes of this defect? How is the presbyopia of a person corrected?

Ans: Presbyopia is a visual impairment mainly due to aging when a person is unable to see the near and far off objects clearly.

The main causes of presbyopia are as follows:

1. Stiffness of the eye lens

2. Due to aging, the power of accommodation of the eye may decrease.

3. The ciliary muscles become weak.

Presbyopia is corrected using a bifocal lens whose upper half has a concave nature and the lower half a convex nature.

5. The rainbow is a natural spectrum appearing in the sky after a rain shower.

a. Is it correct to say that a rainbow is always formed in a direction opposite to the sun?

Ans: Yes, a rainbow is always formed in a direction opposite to the sun as a rainbow is just the sunlight that has been refracted and reflected.

b. Can it be seen on a sunny day?

Ans: Yes, a rainbow can be seen on a sunny day if the Sun’s beam passing through the droplets of water suspended in the atmosphere, reaches the observer’s eye.

c. Arrange the sequence in correct sequential order Refraction, Internal Reflection, Refraction & Dispersion.

Ans: The correct sequential order is:

Refraction & Dispersion, Internal Reflection, Refraction.

6. 

1. Show a diagram to show the correctness of hypermetropia?

Ans: Diagram to show the correctness of hypermetropia is shown below,

7. A reporter records the following observations of an astronaut from his spaceship. Justify each statement.

a. The length of the day is the same as observed on the earth.

Ans: This statement is not true as the length of the day in space can be four minutes shorter than on Earth.

b. Space appears black in colour.

Ans: The statement is correct because in space there is no atmosphere. Hence, there is no scattering of light.

c. The star appears to twinkle while the planets do not do so as they do on the earth.

Ans: The statement is incorrect since we know that the twinkling of stars is due to atmospheric refraction and space has no atmosphere. Hence, the stars do not appear to twinkle in space.

8. Why do stars twinkle?

Ans: Twinkling of stars is due to the atmospheric refraction of light. Stars behave as point sources of light since they are present far away. The path of the light rays from the star experiences atmospheric refraction and the position of the star appear to change. Also, the amount of light entering the eye flickers, so sometimes the star appears brighter and at other times fainter. Thus, the stars twinkle.

9. Explain why the planets do not twinkle.

Ans: The planets are much closer to the earth than the stars. A planet can be considered a collection of a large number of limited light sources. Although light comes from individual point sources flickering, the total amount of light that enters our eye from all of the individual point sources will be the same. Thus, the planets appear equally brighter and there are no planetary blinks.

10. A certain person has a minimum distance of distinct vision of $150$ cm. He wishes to read at a distance of $25$ cm. What focal length glass should he use? What is the nature of eye defects?

Ans: Given,

$\Rightarrow v=-150$ cm

$\Rightarrow u=-25$ cm

From the lens formula, we have: 

$\Rightarrow \dfrac{1}{f}=\dfrac{1}{v}-\dfrac{1}{u}$

$\Rightarrow \dfrac{1}{f}=\dfrac{1}{-150}-\dfrac{1}{-25}$

$\Rightarrow \dfrac{1}{f}=\dfrac{1}{30}$

$\Rightarrow f=30$ cm

Since the focal length is positive, the lens used is a convex lens.

Hence, the eye defect is Hypermetropia.

Long Answer Questions (5 Marks)

1. A $14$-year-old student is not able to clearly see the questions written on the blackboard placed at a distance of $5$ m from him.

a. Name the defect of vision he is suffering from?

Ans: The student is suffering from myopia.

b. Draw the diagram to show this defect?

Ans: The diagram showing the myopic defect is drawn below.

c. Name the type of lens used to correct this defect? 

Ans: A concave lens is used to correct myopia.

d. Name two possible causes of this defect.

Ans: The two possible causes of myopia are:

i. Elongation of the eyeball

ii. Decrease in the focal length of the eye lens

e. Draw the diagram to show how this defect can be corrected.

Ans: The diagram showing how myopic defect is corrected is drawn below.

2. 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.

Ans: The diagram showing the correction of hypermetropia is drawn below.

Near point of a hypermetropic eye is 1 m and that of a normal eye is 25 cm.

Given,

$\Rightarrow v=-1\text{ m = }-100\text{ cm}$

$\Rightarrow u=-25$ cm

From the lens formula, we have: 

$\Rightarrow \dfrac{1}{f}=\dfrac{1}{v}-\dfrac{1}{u}$

$\Rightarrow \dfrac{1}{f}=\dfrac{1}{-100}-\dfrac{1}{-25}$

$\Rightarrow f=\dfrac{100}{3}\text{ cm = }\dfrac{1}{3}\text{ m}$ 

The focal length is given by,

$\Rightarrow f=\dfrac{1}{P}$

$\Rightarrow P=\dfrac{1}{\left( \dfrac{1}{3} \right)}$  D

$\Rightarrow P=+3.0\text{ D}$

Chapter 11 Science Class 10 Important Questions - Free PDF Download

This chapter is crucial in science class 10 since it contains a lot of information. This chapter gives students information on how to prepare for exams and the appropriate quantity of study material to help them revise this topic on the human eye. Students will study about the human eye, different types of lenses, the light spectrum, and the numerous sorts of eye disorders that people experience, as well as how to remedy these problems. Students will study about the human eye and its different components, including the role of cones and rods. 

The notes for this chapter are simply accessible on the Vedantu website. Students may view the human eye class 10 critical questions at any time on the Vedantu website. Students may either download it in pdf format or convert it to doc format. Students can also print these questions for ease of study because gazing at a screen all day can be exhausting, and using a computer can be quite distracting.

CBSE Class 10 Science Chapter 11 Important Concepts 

This chapter is quite vast and covers a lot of concepts on the human eye and the colourful world. So for students to get a better idea of the chapter, they can look at the following important concepts -

Ciliary Muscles 

The ciliary muscles are the muscles that hold the eye in its position and when the muscles relax and contract, they change the shape of the eye lens which in turn changes the focal length of the eye as it can increase and decrease based on the brain's instructions. 

Power of Accommodation of the Eye

This is the power of the eye to change its focal length, and this is done to focus on the rays coming on the retina and the objects that are close by, and this is based on several factors.

The limit of power of accommodation shows that the focal length of the eye cannot be decreased to a certain limit. The near point of the eye is when the eye cannot see the objects that are placed closer than a certain minimum distance.

Sun Appear Reddish in the Morning 

The reason why the sun appears reddish in the morning is that in the early morning the sun is placed on the horizon. Light from the sun passes through thicker layers of air, and all these layers make the sun seem more reddish to the natural eye. 

Stars Twinkle 

Because of various atmospheric refractions from the starlight the stars twinkle. Stars are very far away from us so they seem to be sources of light. The phenomena of atmospheric fractions make these sources of light seem to be varying and therefore the position of the star also seems to fluctuate and so does the amount of light that enters the eye. This is why the stars sometimes appear to be fainter or brighter. 

 Planets Do Not Twinkle 

Planets are seen as an extended source and are much closer to the earth. Therefore plants may be considered sources of light a lot of the time. The light coming from individual point-sized sources flickers but the total amount of light entering our point size flown all point-sized sources seems to average out the constant. Therefore planets are always brighter but don't twinkle as much. 

Why Does the Sky Appear Dark Instead of Blue to Astronauts? 

The sky appears blue because of the scattering of light of a shorter wavelength by particles in the atmosphere to the earth. If the earth had no atmosphere, then the sky would appear blue at all cause there would be no scattering of light. When the astronaut is in space he doesn't see any atmosphere so it appears dark to them.

CBSE Class 10 Science Chapter 11 Important Questions

1. Why does the sky appear dark instead of blue to the astronaut?

2. Explain why planets do not twinkle 

3. Why do stars twinkle 

4. Write two causes of hypermetropia. Show the diagram to correct hypermetropia.

5. What is presbyopia? State the causes of this defect. How is the presbyopia of a person corrected?

6. What is a scattering of the light?

7. What is the range of vision?

8. What is the basic cause of atmospheric refraction?

9. Can visible light be scattered through atoms and molecules in the atmosphere?

10. Why does the sky look blue?

11. What is the spectrum?

12. Why do different colours deviate through different angles when passing through a prism?

13. What is the function of the optic nerve in the human eye?

14. Why are we not able to see things clearly when coming out of a dark room?

15. Why do we observe the wavering or flickering of objects when we are near a fire during the daytime?

16. Why does the sun appear reddish in the morning? 

17. What happens to the image distance in the eye when we increase the distance of an object from the eye?

18. Why is a normal eye not able to see things clearly when the objects are placed closer than 25 cm?   

Benefits of Ch 11 Science Class 10 Important Questions

Pupils must appreciate the significance of this topic and what it holds for sophisticated schoolchildren. Students will be able to get the most on their examinations if they use the relevant questions and follow a strict practice regimen. These examinations might be challenging without good supervision, but by utilising Vedantu, students will be prepared to study in a more organised manner.

The following are the advantages of Chapter 11 Science Class 10 Important Questions:

• Students can use Vedantu to use their time wisely, it helps boost their confidence after consistent practice and students can plan their preparation accordingly.

• It provides students with a structure with which they will study for his or her upcoming examinations.

• This is a fundamental chapter for college kids and plays an important role in upcoming grades.

• The concepts taught in this chapter will help set the basic knowledge on the human eye for students.

• Students studying this subject will also find the notes to be quite handy as well.

• Students don’t need to worry about the relevance of those questions as they're all cross-checked and updated consistently with the newest CBSE guidelines and rules. therefore the information in this article is genuine and reliable.

Conclusion 

This chapter demonstrated the numerous functions of the human eye. The most essential notion in this chapter is how light affects how we view different objects and how the eye processes it. The human eye is extremely complex, and this chapter has demonstrated how it interprets numerous objects. This chapter on the human eye has also provided us with insight into how the human eye perceives different things and how light plays an important role.

This chapter addresses numerous questions that students have about light, such as light dispersion, star twinkling, why planets don't sparkle, and many others. This chapter also explains how concave and convex lenses function in the human eye. Students may utilise this article to make better use of their time; it will enhance students' confidence with constant practise, and students will be able to schedule their preparation properly. Students might work harder to achieve their goals and achieve higher grades. These crucial questions ensure that students are aware of the subject's numerous subjects and are learning.

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