CBSE Class 10 Science Revision Notes Chapter 10 The Human Eye and the Colourful World 2026–27
The human eye uses light to form images on the retina and helps us see objects and colours around us. CBSE Class 10 Science Chapter 10 explains the human eye, vision defects, prism, dispersion, atmospheric refraction and scattering of light.
The Human Eye and the Colourful World explains how the eye forms images and how light creates natural optical phenomena. The chapter connects the lens of the eye with vision defects and explains why the sky appears blue, stars twinkle and rainbows form.
Use these CBSE Class 10 Science Revision Notes Chapter 10 for the 2026–27 academic year to revise eye structure, power of accommodation, myopia, hypermetropia, prism, dispersion of light, atmospheric refraction and scattering. Focus on diagrams, correction lenses and process-based explanations.
Key Takeaways
- Human eye: The eye lens forms a real and inverted image on the retina.
- Accommodation: Ciliary muscles change the focal length of the eye lens.
- Vision defects: Myopia is corrected by a concave lens, and hypermetropia by a convex lens.
- Scattering: Shorter wavelengths scatter more, so the clear sky appears blue.
Struggling with eye diagrams, vision defects, prism dispersion and scattering of light?
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CBSE Class 10 Science Revision Notes Chapter 10 Chapter Overview
The human eye works like a camera. Its lens system forms an image on a light-sensitive screen called the retina.
| Concept | Meaning | Key Example |
| Human eye | Sense organ that enables vision | Seeing objects and colours |
| Accommodation | Adjustment of eye lens focal length | Seeing near and distant objects |
| Vision defect | Blurred vision due to refractive defect | Myopia, hypermetropia |
| Dispersion | Splitting of white light into colours | Spectrum through prism |
| Atmospheric refraction | Bending of light by air layers | Twinkling of stars |
| Scattering of light | Deflection of light by fine particles | Blue sky |
This chapter uses ideas from refraction to explain the eye and natural phenomena. It also explains how lenses correct common vision defects.
Important Topics in CBSE Notes Class 10 Science Chapter 10 Human Eye and Colourful World
Class 10 Science Chapter 10 Notes include both biological structure and physics concepts. The eye, prism and atmosphere are the three main focus areas.
| Important Topic | What to Revise | Key Terms |
| Human eye | Eye parts and image formation | Cornea, iris, retina |
| Power of accommodation | Focal length adjustment | Ciliary muscles, near point |
| Defects of vision | Causes and correction | Myopia, hypermetropia |
| Presbyopia | Age-related near vision problem | Bifocal lens |
| Prism | Refraction through a triangular prism | Angle of deviation |
| Dispersion | Splitting of white light | VIBGYOR, spectrum |
| Atmospheric refraction | Refraction by air layers | Twinkling, sunrise |
| Scattering of light | Deflection by particles | Tyndall effect, blue sky |
Vision defects need a cause-and-correction table. Prism and scattering topics need process-flow revision.
Human Eye Class 10 Notes: Structure and Function of the Eye
The human eye is approximately spherical in shape. Light enters through the cornea and finally forms an image on the retina.
Parts of the Human Eye and Their Functions
| Part of Eye | Function |
| Cornea | Transparent front surface through which light enters |
| Iris | Dark muscular diaphragm that controls pupil size |
| Pupil | Opening that regulates the amount of light entering the eye |
| Eye lens | Focuses light on the retina |
| Ciliary muscles | Change the curvature of the eye lens |
| Retina | Light-sensitive screen where image is formed |
| Optic nerve | Carries electrical signals to the brain |
Most refraction of light entering the eye occurs at the outer surface of the cornea. The eye lens provides finer adjustment of focal length.
Image Formation on the Retina
The eye lens forms an inverted real image of the object on the retina. The retina has many light-sensitive cells.
| Step | What Happens |
| 1 | Light enters through the cornea |
| 2 | Pupil controls the amount of light |
| 3 | Eye lens focuses light on the retina |
| 4 | Retina cells get activated |
| 5 | Electrical signals travel through optic nerves |
| 6 | Brain processes the signals |
The brain interprets the signals so that we perceive objects as they are.
Power of Accommodation in Class 10 Science Chapter 10 Notes
Power of accommodation is the ability of the eye lens to adjust its focal length. This helps the eye focus on objects at different distances.
Near Point, Far Point and Least Distance of Distinct Vision
| Term | Meaning | Normal Value |
| Near point | Nearest point seen clearly without strain | About 25 cm |
| Far point | Farthest point seen clearly | Infinity |
| Least distance of distinct vision | Minimum comfortable clear vision distance | About 25 cm |
When ciliary muscles are relaxed, the eye lens becomes thin. Its focal length increases, so distant objects are seen clearly.
When ciliary muscles contract, the eye lens becomes thicker. Its focal length decreases, so nearby objects are seen clearly.
| Object Position | Ciliary Muscle | Eye Lens | Focal Length |
| Distant object | Relaxed | Thin | Increases |
| Nearby object | Contracted | Thick | Decreases |
A normal eye can see objects clearly between 25 cm and infinity.
Defects of Vision and Correction in Human Eye and Colourful World Class 10 Notes
Defects of vision occur when the eye cannot focus light correctly on the retina. These defects can be corrected using suitable spherical lenses.
Myopia and Its Correction
Myopia is also called near-sightedness. A person with myopia can see nearby objects clearly but cannot see distant objects distinctly.
| Point | Myopia |
| Also called | Near-sightedness |
| Clear vision | Nearby objects |
| Blurred vision | Distant objects |
| Image formed | In front of the retina |
| Causes | Excessive curvature of eye lens or elongation of eyeball |
| Correction | Concave lens |
A concave lens of suitable power brings the image back on the retina. This corrects myopia.
Hypermetropia and Its Correction
Hypermetropia is also called far-sightedness. A person with hypermetropia can see distant objects clearly but cannot see nearby objects distinctly.
| Point | Hypermetropia |
| Also called | Far-sightedness |
| Clear vision | Distant objects |
| Blurred vision | Nearby objects |
| Image formed | Behind the retina |
| Causes | Eye lens focal length too long or eyeball too small |
| Correction | Convex lens |
A convex lens provides additional focusing power. It helps form the image on the retina.
Presbyopia and Cataract
Presbyopia occurs due to ageing. The power of accommodation decreases as ciliary muscles weaken and the eye lens loses flexibility.
| Defect or Condition | Cause | Correction or Treatment |
| Presbyopia | Ageing and reduced accommodation | Suitable corrective lens |
| Myopia with hypermetropia | Need for distant and near vision correction | Bifocal lens |
| Cataract | Eye lens becomes milky and cloudy | Cataract surgery |
A common bifocal lens has a concave upper part for distant vision. Its lower part is convex for near vision.
Refraction Through a Prism in CBSE Class 10 Science Revision Notes Chapter 10
A triangular glass prism has two triangular bases and three rectangular lateral surfaces. The two refracting surfaces are inclined to each other.
When light enters a prism, it bends towards the normal at the first surface. At the second surface, it bends away from the normal.
Angle of Deviation in a Glass Prism
| Term | Meaning |
| Incident ray | Ray entering the prism |
| Refracted ray | Ray travelling inside the prism |
| Emergent ray | Ray coming out of the prism |
| Angle of prism | Angle between two lateral faces |
| Angle of deviation | Angle between incident ray and emergent ray |
The emergent ray bends at an angle to the direction of the incident ray. This angle is called the angle of deviation.
Dispersion of White Light in The Human Eye and the Colourful World Notes
Dispersion is the splitting of white light into its component colours. A glass prism splits white light into a band of seven colours.
VIBGYOR and Recombination of White Light
The colours in the spectrum are arranged as VIBGYOR.
| Letter | Colour |
| V | Violet |
| I | Indigo |
| B | Blue |
| G | Green |
| Y | Yellow |
| O | Orange |
| R | Red |
Different colours bend through different angles in a prism. Red bends the least, while violet bends the most.
Newton used a prism to obtain the spectrum of sunlight. He also showed that the seven colours can recombine to form white light.
Rainbow Formation in Class 10 Science Chapter 10 Notes
A rainbow is a natural spectrum formed in the sky after rain. Water droplets act like tiny prisms.
| Step | Process in Water Droplet |
| 1 | Sunlight enters a water droplet |
| 2 | Light refracts inside the droplet |
| 3 | Light disperses into colours |
| 4 | Internal reflection occurs |
| 5 | Light refracts again while coming out |
A rainbow is usually seen in the direction opposite to the Sun. It appears when sunlight passes through tiny water droplets present in the atmosphere.
Atmospheric Refraction in CBSE Notes Class 10 Science Chapter 10
Atmospheric refraction is the refraction of light by the Earth’s atmosphere. It occurs because the refractive index of air changes gradually in different layers.
Twinkling of Stars
Stars appear to twinkle due to atmospheric refraction. Starlight passes through layers of air before reaching our eyes.
| Reason | Explanation |
| Star is far away | It behaves like a point source of light |
| Air layers keep changing | Refractive index changes continuously |
| Apparent position changes | Light appears to come from slightly different positions |
| Brightness changes | Amount of starlight entering the eye varies |
Planets usually do not twinkle because they appear as extended sources of light. Variations from different points average out.
Advance Sunrise and Delayed Sunset
The Sun is visible before actual sunrise and after actual sunset due to atmospheric refraction. The atmosphere bends sunlight and makes the Sun appear higher than its actual position.
| Phenomenon | Cause |
| Advance sunrise | Sun appears visible before it reaches the horizon |
| Delayed sunset | Sun remains visible after going below the horizon |
| Apparent shift | Atmospheric refraction raises the apparent position |
The apparent shift is about half a degree. This gives about two minutes of advance sunrise and about two minutes of delayed sunset.
Scattering of Light in Human Eye and Colourful World Class 10 Notes
Scattering of light is the deflection of light by particles in a medium. The amount of scattering depends on particle size and wavelength of light.
Tyndall Effect
Tyndall effect is the scattering of light by colloidal particles. It makes the path of light visible.
| Example | Why Path Becomes Visible |
| Sunlight in a dusty room | Dust particles scatter light |
| Light passing through smoke | Smoke particles scatter light |
| Light through colloidal solution | Colloidal particles scatter light |
Very fine particles scatter shorter wavelengths more strongly. This explains several colour effects in the sky.
Why the Sky Appears Blue and the Sun Appears Red
The sky appears blue because molecules in air scatter blue light more than red light. Blue light has a shorter wavelength.
| Phenomenon | Explanation |
| Blue sky | Fine particles scatter shorter blue wavelengths strongly |
| White clouds | Larger particles scatter all colours nearly equally |
| Red sunrise and sunset | Sunlight travels a longer path through the atmosphere |
| Red danger signals | Red light scatters less and travels farther |
During sunrise and sunset, sunlight travels through a thicker layer of air. Most shorter wavelengths scatter away, so red light reaches our eyes.
Important Points of Class 10 Science Chapter 10 Human Eye and Colourful World
These quick notes cover the main facts from Human Eye and Colourful World Class 10 Notes.
| Concept | Important Point |
| Human eye | Forms a real and inverted image on retina |
| Cornea | Most refraction occurs at its outer surface |
| Iris | Controls pupil size |
| Pupil | Controls light entry |
| Retina | Contains light-sensitive cells |
| Accommodation | Eye lens changes focal length |
| Near point | About 25 cm for a normal young adult |
| Far point | Infinity for a normal eye |
| Myopia | Corrected by concave lens |
| Hypermetropia | Corrected by convex lens |
| Presbyopia | Caused by reduced accommodation with ageing |
| Prism | Bends emergent ray away from incident direction |
| Dispersion | Splitting of white light into seven colours |
| Atmospheric refraction | Causes twinkling and apparent Sun shift |
| Scattering | Explains blue sky and red sunset |
Useful Links for Class 10 Science
| Section | Useful Links |
| NCERT Solutions | NCERT Solutions for Class 10 Science |
| Important Questions | Important Questions Class 10 Science |
| Previous Year Papers | CBSE Science Question Paper Class 10 |
| NCERT Books | NCERT Books for Class 10 Science |
| Revision Notes | CBSE Class 10 Science Revision Notes |
| Syllabus | CBSE Class 10 Science Syllabus |
| Sample Papers | CBSE Sample Papers for Class 10 Science |
CBSE Class 10 Science Revision Notes
FAQs (Frequently Asked Questions)
Power of accommodation is the ability of the eye lens to change its focal length. Ciliary muscles help the lens become thin for distant objects and thick for nearby objects.
Myopia is corrected using a concave lens. In myopia, distant objects appear blurred because the image forms in front of the retina. A concave lens brings the image back on the retina.
Hypermetropia is corrected using a convex lens. In this defect, nearby objects appear blurred because the image forms behind the retina. A convex lens gives extra focusing power.
Dispersion is the splitting of white light into seven colours. A glass prism separates white light into violet, indigo, blue, green, yellow, orange and red.
The sky appears blue because air molecules scatter shorter blue wavelengths more strongly than longer red wavelengths. This scattered blue light reaches our eyes from different directions.