Aakash Repeater Courses
ApplyTake Aakash iACST and get instant scholarship on coaching programs.
Ever wondered how we see the world around us or why the sky looks blue and sunsets appear red? All these answers lie in Class 10 Science Chapter 10: The Human Eye and the Colourful World. This chapter explains how the human eye works, how we see objects and what are the reasons for beautiful phenomena such as rainbows, twinkling stars and the colours in the sky. It is a very important chapter for board exams and science olympiads like NSO and NSEJS etc. These NCERT notes for class 10 science are prepared by subject experts as per the latest CBSE syllabus.
These Class 10 NCERT notes are written in easy to understand language and cover important topics such as the structure and functioning of the human eye, power of accommodation, defects of vision and their correction using lenses. These NCERT Notes also explain concepts like refraction through a prism, dispersion of light, and scattering of light using real-life examples.
Also Read
The focal lens of the lens in the eye can be decreased or increased. The eye lens gets thin when muscles are relaxed. This results in increased focal length. It helps to see distant objects. And when the eye lens becomes thick, the focal length is decreased and we see nearby objects.
Power of accommodation is the ability of the eye lens to adjust the focal length.
The near Point of the Eye is at 25 cm and the Far Point of the Eye is infinity.
In old age, the lens becomes milky and cloudy, this is called a Cataract. This leads to complete or partial loss of vision.
The three common defects of vision are:
Myopia (Nearsightedness): In this, distant objects cannot be seen clearly, but nearby objects are visible.
Light from a far object forms an image before it reaches the retina.
Corrected using concave lens.
Hypermetropia (Far-sightedness): Nearby objects are seen clearly whereas distant objects can not be seen clearly.
Image of a nearby object is formed behind the retina.
Corrected using a convex lens.
Presbyopia: The power of accommodation decreases with ageing. They have difficulty in near vision as well as far vision. Bifocal lenses are used to correct the defects.
A glass prism is a refracting medium with two or more non-parallel refracting surfaces. It is named according to the shape of its base. The prism shown below is a triangular prism which has two triangular bases and three rectangular lateral surfaces. For a triangular glass prism, the angle between the non-parallel (lateral) refracting surfaces is known as the angle of the prism denoted by
When light passes through a prism as shown in figure below, it gets deviated and the angle between the emergent ray and the incident ray is called angle of deviation (
When light falls on the prism, the prism splits the incident light into a band of seven colours. The colours observed are VIBGYOR (Violet, Indigo, Blue, Green, Yellow, Orange and Red). The band of colour is Spectrum. Thus, the splitting of incident light into different colours is Dispersion. The splitting is because of the bending of light rays at different angles. Violet light bends the most, whereas red light bends the least.
1 more prism is placed in an inverted position to get back the white light
The phenomenon of a rainbow is also because of the dispersion of light.
With height, the layers of the atmosphere changes, so does its optical density, hence light on entering the earth's atmosphere undergoes refraction continuously. The refraction of light by the earth's atmosphere is termed as atmospheric refraction. Now, let us see few phenomena occurring in nature due to the atmospheric refraction of light.
When a star is lit in the atmosphere, it has to undergo refraction. The refractive index changes and the light bends towards the normal. As a result, the actual position of the star is a little bit different from its apparent position. We also know that the atmosphere of the earth is not stationary, so changes in the apparent position of the stars occur. Thus, we see them twinkling in the sky or the Earth’s atmosphere.
Due to the phenomenon of atmospheric refraction, the sun is visible 2 minutes before the actual sunrise, which is known as advanced sunlight. Just like the sunrise, the Sun is also visible 2 minutes after the actual sunset has taken place. This is known as Delayed Sunset.
When sunlight falls on a mixture of minute particles (like smoke, tiny water droplets, suspended particles of dust and molecules of air in the earth's atmosphere), it gets scattered in all directions, if the size of the particle is comparable to the wavelength of light. These particles are more effective in scattering light of shorter wavelength at the blue end than light of longer wavelength at the red end.
Tyndall Effect
When a beam of light strikes tiny water droplets and suspended particles of dust the path of the beam becomes visible. This is the Tyndall Effect. Fine particles scatter, and particles of larger size scatter light of longer wavelengths.
The colour of the sky appears blue because of the scattering of light. When the sunlight passes through the atmosphere, the fine particles present in the air will scatter the blue colour since it has a shorter wavelength.
When the Sun rises and sets, its light which is present near the horizon passes through thicker layers of atmosphere and travels larger distances before reaching our eyesight. When the light of the Sun present overhead travels a comparatively shorter distance than light from the horizon, it results in the white appearance of the sun. Near the horizon, most of the blue light and shorter wavelengths are scattered by the particles. Therefore, the red light that reaches our eyes as it has the longest wavelength, hence the sky appears reddish.
The main topics covered in Chapter 10 of NCERT for Class 10 Science are
Eye
Defects of eye
Dispersion of light
Total internal reflection of light
As mentioned in the CBSE Class 10 Science chapter 10 notes, blue light scatters more because of its shorter wavelength and the sky appears blue
Myopia ( NearSightedness): distant objects cannot be seen clearly but nearby objects are clearly visible.
The Tyndall effect refers to the scattering of light by colloidal particles or larger particles suspended in a transparent medium, making the beam of light visible as it passes through.
It means the eye can focus on near and far things by changing the lens shape.
Take Aakash iACST and get instant scholarship on coaching programs.
This ebook serves as a valuable study guide for NEET 2025 exam.
This e-book offers NEET PYQ and serves as an indispensable NEET study material.
As per latest syllabus. Physics formulas, equations, & laws of class 11 & 12th chapters
As per latest syllabus. Chemistry formulas, equations, & laws of class 11 & 12th chapters
As per latest 2024 syllabus. Study 40% syllabus and score upto 100% marks in JEE