CBSE Class 8 > Class 8 Notes > Year 8 Physics (Cambridge) > Light
Light
Introduction to Light
Light is a form of energy that enables us to see the world around us. It travels in straight lines and can move through different mediums such as air, water, and glass.
Properties of Light
- Speed of Light: Light travels extremely fast at a speed of about 300,000 kilometers per second in a vacuum.
- Reflection: When light hits a surface, it can bounce back. This is known as reflection. Smooth, shiny surfaces like mirrors reflect light well.
- Refraction: Light can bend when it passes from one medium to another, such as from air to water. This bending is called refraction.
- Absorption: Some materials can absorb light, converting it into heat. Dark surfaces absorb more light than light-colored surfaces.
Examples of Light Properties
- Reflection: When you look in a mirror, you see your reflection because the light from your face hits the mirror and bounces back to your eyes.
- Refraction: A straw appears bent when it is placed in a glass of water due to the refraction of light.
MULTIPLE CHOICE QUESTIONTry yourself: Which property of light causes a straw to appear bent when placed in a glass of water?
Coloured Light
How We See Colors
We see different colors because of the way light interacts with objects and our eyes. White light, like sunlight, is made up of all the colors of the spectrum: red, orange, yellow, green, blue, indigo, and violet.
Dispersion of Light
When white light passes through a prism, it separates into its component colors. This process is called dispersion. The colors spread out to form a spectrum, which is often seen in a rainbow.
Color Absorption and Reflection
Objects appear a certain color because they reflect that color of light and absorb the other colors.
For example:
- A red apple looks red because it reflects red light and absorbs other colors.
- A blue sky appears blue because molecules in the air scatter blue light from the sun more than they scatter red light.
Mixing Colors
- Primary Colors of Light: Red, green, and blue are the primary colors of light. By mixing these colors in different combinations, we can create other colors.
- Secondary Colors: When two primary colors are mixed, they form secondary colors.
For example:- Red and green make yellow.
- Green and blue make cyan.
- Blue and red make magenta.
Examples of Color Mixing
- Television and Computer Screens: These screens use tiny pixels of red, green, and blue light to create the wide range of colors we see.
- Stage Lighting: Stage lights often use colored gels to mix different colors of light to create mood and atmosphere in a theater production.
Summary
Light is a fascinating and essential part of our world, enabling us to see and experience colors. Understanding the properties of light, such as reflection, refraction, and absorption, helps us to comprehend how we see and interact with our environment. Coloured light, with its primary and secondary colors, plays a crucial role in everything from technology to nature, making our visual experiences vibrant and diverse.
The document Light is a part of the Class 8 Course Year 8 Physics (Cambridge).
All you need of Class 8 at this link: Class 8
FAQs on Light
| 1. What is light and how does it travel in Class 8 Physics? |  |
Ans. Light is a form of energy that travels in straight lines at incredibly fast speeds (about 300,000 km/s in vacuum). It behaves as both waves and particles. In Class 8, students learn that light propagates through transparent media like air and glass, and this rectilinear motion of light explains why shadows form sharp edges and why light rays cast distinct shadows.
| 2. How do mirrors reflect light and what's the difference between plane and curved mirrors? | |
Ans. Mirrors reflect light following the law of reflection: the angle of incidence equals the angle of reflection. Plane mirrors produce virtual, upright images of the same size as objects. Curved mirrors-either concave or convex-bend reflected rays differently: concave mirrors can magnify objects, while convex mirrors create diminished, wider field-of-view images used in vehicle rear-view applications.
| 3. Why do objects appear different colours and how does light refraction work? | |
Ans. Objects appear coloured because they absorb certain wavelengths of light and reflect others. Refraction occurs when light enters a denser medium (like glass or water) and bends from its original path, changing speed and direction. This bending explains why objects underwater appear closer than they actually are and why lenses focus light to form magnified or diminished images.
| 4. What's the difference between real and virtual images formed by lenses and mirrors? | |
Ans. Real images form where light rays converge-they're inverted, can be projected onto a screen, and appear in front of mirrors or behind converging lenses. Virtual images form where light rays appear to diverge-they're upright, cannot be projected, and appear behind plane mirrors or in front of diverging lenses. Understanding image formation helps explain how cameras, magnifying glasses, and eyeglasses work differently.
| 5. How does the human eye focus light and what causes common vision defects like myopia? | |
Ans. The eye's lens adjusts its curvature to focus light precisely onto the retina, forming clear images. In myopia (short-sightedness), the eye focuses light in front of the retina, making distant objects blurry-corrected using concave lenses. Hyperopia (long-sightedness) occurs when light focuses behind the retina; convex lenses correct this. Students can refer to mind maps and visual diagrams on EduRev to understand eye anatomy and lens correction principles clearly.
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Apr 20, 2026 Last updated
Document Description: Light for Class 8 2026 is part of Year 8 Physics (Cambridge) preparation. The notes and questions for Light have been prepared according to the Class 8 exam syllabus. Information about Light covers topics like and Light Example, for Class 8 2026 Exam. Find important definitions, questions, notes, meanings, examples, exercises and tests below for Light.
Introduction of Light in English is available as part of our Year 8 Physics (Cambridge) for Class 8 & Light in Hindi for Year 8 Physics (Cambridge) course. Download more important topics related with notes, lectures and mock test series for Class 8 Exam by signing up for free. Class 8: Light
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Light of Year 8 Physics covers all the important topics, helping you prepare for the Class 8 exam on EduRev. Start for free!
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In this doc you can find the meaning of Light defined & explained in the simplest way possible. Besides explaining types of Light theory, EduRev gives you an ample number of questions to practice Light tests, examples and also practice Class 8 tests
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