CBSE Class 10 Science: The Human Eye and the Colourful World | Important Concept-Based Questions
CBSE Class 10 Science: The Human Eye and the Colourful World
Important Concept-Based Questions | BACE IIT JEE Blog
🔷 Introduction
The Human Eye and the Colourful World is one of the most fascinating chapters in CBSE Class 10 Science. It beautifully blends biology and physics to explain how we see the world around us — and why it appears so full of vibrant colours! This chapter also introduces optical phenomena like refraction, dispersion, scattering and defects of vision.
Understanding these concepts not only helps in scoring well in the exam but also builds foundational knowledge for higher studies in physics, medicine, and engineering. At BACE IIT JEE, our goal is to simplify these scientific concepts so that students can learn them conceptually and apply them confidently in board exams.
🌞 The Structure and Functioning of the Human Eye
The human eye is often compared to a camera because it captures light rays, focuses them, and forms a real image on the retina. Let’s explore its key parts:
- Cornea: The transparent front part that refracts light entering the eye.
- Iris: The coloured part controlling the size of the pupil.
- Pupil: Regulates the amount of light entering the eye.
- Lens: A convex lens that adjusts shape to focus light precisely on the retina.
- Retina: Contains light-sensitive cells that convert light into electrical signals.
- Optic Nerve: Transmits visual information from retina to the brain.
The ability of the lens to adjust its focal length is known as accommodation. This enables us to view nearby and distant objects clearly.
✨ Concept Tip:
The least distance of distinct vision for a normal human eye is 25 cm. The near point is 25 cm and the far point is infinity.
👁️ Defects of Vision and Their Correction
Sometimes, the eye loses its ability to focus light properly on the retina, leading to vision defects. The three most common are:
- Myopia (Near-sightedness): The person can see nearby objects clearly but distant objects appear blurred.
It occurs when the image forms in front of the retina.
Correction: Using a concave lens. - Hypermetropia (Far-sightedness): The person can see distant objects clearly but nearby objects appear blurred.
It occurs when the image forms behind the retina.
Correction: Using a convex lens. - Presbyopia: Caused due to loss of accommodation power with age. Corrected using bifocal lenses.
Answer: Because it diverges light rays before they enter the eye, allowing the image to form on the retina instead of in front of it.
🌈 The Colourful World — Dispersion and Scattering of Light
After learning how we see, let’s understand how nature creates colours. The world around us appears colourful due to the phenomena of dispersion and scattering.
1️⃣ Dispersion of Light
Dispersion is the process of splitting white light into its seven constituent colours (Violet, Indigo, Blue, Green, Yellow, Orange, Red — VIBGYOR) when passed through a prism. This happens because different colours have different wavelengths and refract by different amounts.
2️⃣ Scattering of Light
Scattering occurs when light interacts with small particles in the atmosphere. The amount of scattering depends inversely on the wavelength of light. Blue light, having a shorter wavelength, scatters more than red light — which explains why the sky appears blue.
Answer: During the day, shorter blue wavelengths scatter more, making the sky appear blue. During sunrise and sunset, sunlight travels a longer path through the atmosphere, scattering away blue light, leaving red and orange hues visible.
🌦️ Atmospheric Refraction and Natural Phenomena
Atmospheric refraction is responsible for many natural optical illusions we experience every day:
- Twinkling of Stars: Due to continuous refraction of starlight through different air layers.
- Advanced Sunrise and Delayed Sunset: Sunlight bends as it passes through the atmosphere, making the sun visible before it rises and after it sets.
- Rainbows: Formed due to dispersion, refraction, and reflection of sunlight in water droplets.
Answer: When sunlight passes through water droplets, it refracts, reflects, and disperses to form a spectrum — creating a rainbow.
🧠 Important NCERT & Board-Based Questions
Below are a few important conceptual and exam-oriented questions you must practice:
- Explain the mechanism of accommodation in the human eye.
- Why do stars twinkle while planets don’t?
- What causes the dispersion of white light through a prism?
- Define the least distance of distinct vision and its significance.
- How does the eye lens form an image on the retina?
- What is presbyopia? How can it be corrected?
- Why do we see a rainbow only after rain?
Answer: Ciliary muscles control the curvature of the lens to adjust its focal length for focusing objects at varying distances.
🔍 Summary of Key Concepts
| Concept | Key Idea |
|---|---|
| Accommodation | Adjusting lens curvature to focus on near/far objects. |
| Myopia | Short-sightedness corrected by concave lens. |
| Hypermetropia | Long-sightedness corrected by convex lens. |
| Dispersion | Splitting of white light into VIBGYOR. |
| Scattering | Shorter wavelengths scatter more; sky appears blue. |
| Rainbow | Formed due to refraction, reflection, and dispersion of light in raindrops. |
💡 Quick Revision Tips
- Revise the diagram of the human eye thoroughly — it is frequently asked.
- Practice ray diagrams for myopia and hypermetropia corrections.
- Understand the difference between refraction and dispersion.
- Use real-life examples like spectacles, rainbow, or camera lenses to relate to concepts.
- Try solving NCERT exemplar and PYQs regularly.
📘 Why Study with BACE IIT JEE?
At BACE IIT JEE, we provide more than textbook learning. Our science mentors ensure:
- Concept clarity through visualization and experiments.
- Regular mock tests and topic-wise quizzes.
- Step-by-step solutions for NCERT and previous-year board questions.
- Individual guidance for students struggling in physics and optics topics.
Our results speak for themselves — students from BACE IIT JEE have consistently topped school boards and secured positions in top engineering and medical entrance exams.
🚀 Final Thoughts
The chapter “The Human Eye and the Colourful World” helps students appreciate both the science of vision and the beauty of the world around them. Understanding its concepts will make light behaviour, refraction, and colours much clearer — setting the base for higher studies in optics and physics.
Stay curious, keep experimenting, and remember — science is not just about memorising; it’s about exploring the world with wonder!
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