NCERT Solutions Class 10 Science Chapter 10 Human Eye and Colorful World

NCERT Solutions Class 10 Science Chapter 10 offers comprehensive and simple concepts for students about the human eye, its various parts, defects of vision problems along with light dispersion, scattering of light and refraction through the atmosphere.

In this NCERT Solutions Class 10 Science Chapter, students will be able to learn how the human eye works, the causes of vision impairment such as myopia and hypermetropia, and the ways of correcting vision defects by prescribing different types of lenses. The NCERT Solutions for class 10 science Chapter 10 Human Eye and Colorful World also include concepts like how rainbows are formed, why the sky appears to be colored, and why stars twinkle, making it easier for kids to understand new ideas while being fun. Engaging in these solutions makes students enhance their problem-solving abilities, sharpen their understanding of difficult ideas, and prepare them for the exams.

1.0Download Class 10 Science Chapter 10 Human Eye and Colorful World NCERT Solutions: Free PDF

You can download the NCERT solutions class 10 science ch 10 pdf from the table above, which can be downloaded so students can access these anywhere and anytime.

2.0NCERT Solutions Class 10 Science Chapter 10 Human Eye and Colorful Science: Overview

Light enters the eye through the tough, clear cornea, which protects the human eye. The iris, a muscle behind the cornea, adjusts the pupil size to control the amount of light entering the eye. The iris also gives the eye its color, such as black, brown, or green. Behind the pupil, the lens further focuses light onto the retina, which contains nerve cell that convert images into signals sent to the brain via the optic nerve. The two types of nerve cells are:

1. Cones – responsible for color and bright light vision.
2. Rods – sensitive to dim light.

In low light, the pupil expands to let in more light, while in bright light, it contracts.

Eye Care Tips:

• To avoid strain, ensure proper lighting for activities, and maintain a reading distance of about 25 cm.
• Wash your eyes regularly with clean water and avoid rubbing them.
• Eat foods rich in Vitamin A, like carrots, leafy greens, eggs, and dairy, to support eye health.
• If you experience pain, irritation, or vision issues, consult a doctor and use corrective lenses if needed.

3.0What Will Students Learn in Chapter 10: Human Eye and Colorful World?

• Learning what the different parts of the eye do and what they do in helping us to see.
• In NCERT Solutions Class 10 Science Chapter 10 there is a brief overview of some of the common vision disorders including myopia which is also known as nearsightedness, hypermetropia or farsightedness and presbyopia, and using lenses.
• How the eye is able to change its ability to focus to accommodate nearby or distant visuals.
• How different colors of white light are formed or separated as it passes through a prism.
• Some of the occurrences such as the twinkling of star and the apparent changes in the path of light due to the atmosphere.
• Learning how the sky appears to be blue, and why the Sun appears reddish during sunrise and sunset.

4.0Class 10 Science Chapter 10 Human Eye and Colorful World NCERT : Detailed Solutions

1. What is meant by the power of accommodation of the eye?

Solution

The ability of the eye lens to adjust its focal length is called power of accommodation.

2. 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?

Solution

To correct this defect of vision, he must use a concave lens.

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

Solution

The far point of a human eye with normal vision is at infinity while the near point is at 25 cm from the eye.

4. A student has difficulty reading the blackboard while sitting in the last row. What could be the defect the student is suffering from? How can it be corrected?

Solution

The student is suffering from eye defect 'myopia'. This defect can be corrected by using a concave lens.

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

(a) presbyopia.

(b) accommodation.

(c) near-sightedness.

(d) far-sightedness.

Solution

Option (b) is correct. The human eye can change the focal length of the eye lens to see the objects situated at various distances from the eye. This ability of the eye is called accommodation.

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

(a) cornea

(b) iris

(c) pupil

(d) retina

Solution

Option (d) is correct. The human eye is like a camera. Its lens system forms an image on a light-sensitive screen called the retina.

7. The least distance of distinct vision for a young adult with normal vision is about

(a) 25 m

(b) 2.5 cm

(c) 25 cm

(d) 2.5 m

Solution

Option (c) is correct.

The least distance of distinct vision is the minimum distance of an object to see a clear image. It is 25 cm for a young adult with normal vision.

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

(a) pupil

(b) retina

(c) ciliary muscles

(d) iris

Solution

Option (c) is correct.

By relaxation or contraction of ciliary muscles, the curvature of the eye lens changes which eventually changes the focal length of the eye lens.

9. A person needs a lens of power -5.5 dioptres for correcting his distant vision. For correcting his near vision, he needs a lens of power +1.5 dioptre. What is the focal length of the lens required for correcting (i) distant vision, and (ii) near vision?

Solution

(i) Focal length f is given by,

f = 1/P

or f = 1/(-5.5) = -0.1818 m

= -18.18 cm

(ii) Focal length f is given by,

f = 1/P

or f = 1/(+1.5) = +0.6667 m

= +66.67 cm

10. 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?

Solution

For myopia, focal length is given by,

f = -x = -80 cm = -0.8 m

Power, P = 1/f = 1/(-0.8)

= -1.25 dioptres.

The lens is a concave lens.

11. 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.

Solution

Here, y = 1 m

1/f = 1/0.25 - 1/y = 1/0.25 - 1/1

= 100/25 - 1 = 4 - 1 = +3

or f = +(1/3) = +0.3333 m = +33.33 cm

Power, P = 1/f = +3 dioptres.

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

Solution

A normal eye is unable to clearly see objects placed closer than 25 cm because the ciliary muscles of eyes are unable to contract beyond a certain limit. If the object is placed at a distance less than 25 cm from the eye, then the object appears blurred and produces strain in the eyes.

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

Solution

The size of the eye cannot be increased or decreased. Therefore, the image distance remains constant. When we increase the distance of an object from the eye, the image distance in the eye does not change. The increase in the object distance is compensated by the change (increase) in the focal length of the eye lens such that the image is formed at the retina of the eye.

14. Why do stars twinkle?

Solution

Twinkling of stars can be seen on a clear night. This is due to atmospheric refraction of light coming from the stars (star light). As the star light enters into the earth's atmosphere, atmospheric refraction takes place due to gradually changing refractive index of the air. Since the physical conditions of the refracting medium (earth's atmosphere) are not stationary, star light flux (luminous flux) entering the eye of an observer continuously fluctuates. This means luminous energy entering the eyes per second from the star increases and decreases with time. Thus, the star sometimes appears brighter and at other times fainter, causing the 'twinkling of stars'.

15. Explain why the planets do not twinkle.

Solution

The apparent size of stars is very small as compared to the apparent size of planets. Thus, the star may be considered as a 

The variable atmospheric conditions are unable to create variations in light flux from the planet entering our eye and thus, planets do not twinkle.

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

Solution

In the morning, the sun is near the horizon. Light reaching the eye of an observer travels a larger distance in the atmosphere. Thus, most of the blue light and shorter wavelength rays are scattered away by the air particles. Hence, the light that reaches the eye of an observer is of longer wavelengths (of red end). Thus, the sun appears reddish at sunrise or sunset.

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

Solution

The sky appears dark instead of blue to an astronaut because there is no atmosphere in outer space that can scatter the sunlight. As the sunlight is not scattered, no scattered light reaches the eyes of the astronauts and the sky appears black to them.

5.0Benefits of Human Eye and Colorful World

1.Understanding of Vision: This chapter helps in understanding how the human eye functions to provide vision, an essential sense for day-to-day activities.

2.Role in Everyday Life: By learning how the Human Eye and Colorful World adapts to different light conditions (like during night or day), students understand its importance in daily tasks.

3.Foundation for Higher Studies: The concepts of refraction and optics introduced in this chapter lay the foundation for more advanced studies in physics and medical sciences, particularly in optometry and vision science.

4.Understanding of Optical Instruments: It helps students comprehend how optical instruments such as cameras and corrective lenses function, which is valuable in both academic and practical settings.

5.Explanation of Light Behavior: It explains the behavior of light, such as rainbows, refraction, dispersion, scattering of light and image formation, which are fundamental concepts in physics.

6.Health Awareness: The chapter promotes awareness about the health of the eyes and the importance of proper eye care and safety, which can be applied to prevent common vision problems.

7.Understanding of Eye Defects: The chapter covers eye defects like myopia, hypermetropia, and astigmatism, and their corrective measures, helping in the practical application of knowledge to improve vision.

8.Awareness of Eye Care:The chapter emphasizes the importance of proper eye care, eye safety, and preventing vision-related problems, which is valuable knowledge for maintaining good health.