Grade 9
  1. Mechanics  1.1. Motion  1.1.1. Types of motion  1.1.2. Distance and displacement  1.1.3. Speed and Velocity  1.1.4. Acceleration  1.1.5. Graphical representation of motion  1.1.6. Equations of motion  1.1.7. Uniform and non-uniform motion  1.1.8. Free fall and acceleration due to gravity  1.1.9. Relative speed  1.1.10. Circular motion  1.2. Laws of force and motion  1.2.1. The concept of force  1.2.2. newton's first law of motion  1.2.3. Newton's second law of motion  1.2.4. Newton's third law of motion  1.2.5. Inertia and types of inertia  1.2.6. Motion  1.2.7. Conservation of momentum  1.2.8. Application of Newton's laws in daily life  1.2.9. Types of Forces (Contact and Non-Contact)  1.2.10. Friction and its effects  1.3. Gravitational force  1.3.1. Newton's law of universal gravitation  1.3.2. Importance of Gravitational Force  1.3.3. Acceleration due to gravity  1.3.4. Free fall and weightlessness  1.3.5. Mass and weight  1.3.6. Variation of g with height and depth  1.3.7. Kepler's laws of planetary motion  1.3.8. Satellites and their orbits  1.4. Work, Energy and Power  1.4.1. Concept of work  1.4.2. Positive and negative actions  1.4.3. Work done by constant and variable force  1.4.4. Energy and its forms  1.4.5. Kinetic energy and potential energy  1.4.6. Law of conservation of energy  1.4.8. Commercial unit of energy  1.4.9. Work–energy theorem  1.5. Simple machines  1.5.1. Types of simple machines  1.5.2. Mechanical advantage  1.5.3. Machine efficiency  1.5.4. Levers and their types  1.5.5. Pulleys and Inclined Planes  1.5.6. Gears and their uses
  2. Properties of matter  2.1. States of matter  2.1.1. Solids, liquids and gases  2.1.2. Properties of different states of matter  2.1.3. Change in state of matter  2.1.4. Plasma and Bose–Einstein condensate  2.2. Density and pressure  2.2.1. Concept of density and relative density  2.2.2. Pressure in solids, liquids and gases  2.2.3. Pascal's law and its applications  2.2.4. Atmospheric pressure and its variations  2.2.5. Surface tension and capillarity  2.3. Buoyancy and Archimedes' principle  2.3.1. Buoyant force  2.3.2. Archimedes principle  2.3.3. Applications of Archimedes' Principle  2.3.4. floating and sinking objects  2.3.5. Theory of Flotation and Archimedes' Principle
  3. Heat and Thermodynamics  3.1. Temperature and heat  3.1.1. Concept of heat and temperature  3.1.2. Temperature measurement  3.1.3. Temperature scales  3.2. Heat transfer  3.2.1. Conduction of heat  3.2.2. Convection of heat  3.2.3. heat radiation  3.2.4. Applications of heat transfer  3.2.5. Thermal conductivity  3.3. Thermal expansion  3.3.1. Expansion of solids, liquids and gases  3.3.2. Abnormal expansion of water  3.3.3. Applications of Thermal Expansion  3.4. Specific heat capacity and latent heat  3.4.1. Concept of specific heat capacity  3.4.2. Measurement and applications of specific heat  3.4.3. Latent heat of fusion and vaporization  3.4.4. Heat Engines and Efficiency
  4. Waves and sound  4.1. Waves and their types  4.1.1. Mechanical and electromagnetic waves  4.1.2. Longitudinal and Transverse Waves  4.1.3. Properties of Waves  4.1.4. Wavelength, frequency and speed of the wave  4.1.5. Superimposition of waves  4.2. Sound waves  4.2.1. Nature and transmission of sound  4.2.2. Speed of sound in different mediums  4.2.3. Reflection of sound and echo  4.2.4. Sonar and ultrasound  4.2.5. Resonance and pulsation  4.3. Sound characteristics  4.3.1. Intensity, loudness and quality of sound  4.3.2. Doppler effect in sound
  5. Lighting and Optics  5.1. Reflection of light  5.1.1. Laws of reflection  5.1.2. Reflection from a plane mirror  5.1.3. Reflection from a spherical mirror  5.1.4. Image formation by concave and convex mirrors  5.1.5. Applications of Reflection  5.2. Refraction of light  5.2.1. Laws of refraction  5.2.2. Refractive index  5.2.3. Refraction through a glass slab  5.2.4. Refraction in water and air  5.2.5. Lenses and their types  5.2.6. Image formation by convex and concave lenses  5.2.7. Total internal reflection and its applications  5.3. Dispersion and scattering of light  5.3.1. Spectrum of white light  5.3.2. Prisms and Dispersion  5.3.3. Tyndall effect and blue sky
  6. Electricity and Magnetism  6.1. Electric charge and static electricity  6.1.1. The concept of electric charge  6.1.2. Charging by friction, contact and induction  6.1.3. Electroscope and its working  6.2. Current Electricity  6.2.1. The concept of electric current  6.2.2. Ohm's Law and Resistance  6.2.3. Factors affecting resistance  6.2.4. Series and Parallel Circuits  6.2.5. Heating effect of electric current  6.2.6. Electric power and energy  6.3. Magnetism  6.3.1. Natural and artificial magnets  6.3.2. Properties of magnets  6.3.3. Earth's magnetism  6.3.4. Magnetic field and field lines  6.3.5. Electromagnets and their applications
  7. Modern Physics  7.1. structure of the atom  7.1.1. Atomic Structure and Subatomic Particles  7.1.2. Electrons, Protons, and Neutrons  7.1.3. Rutherford and Bohr model  7.2. Radioactivity  7.2.1. Types of radioactive emissions  7.2.2. Half-life and radioactive decay  7.2.3. Uses and Hazards of Radioactivity
  8. Space science and astronomy  8.1. The universe and its components  8.1.1. Stars and galaxies  8.1.2. Planets and Solar System  8.2. Satellites  8.2.1. Natural and artificial satellites  8.2.2. Use of satellites

Grade 9 → Lighting and Optics ↓


Refraction of light


Refraction of light is a fascinating phenomenon that occurs when light passes from one medium to another. It is seen in many different ways in everyday life. This document will walk you through the fundamental concepts of refraction, including visual examples and easy-to-understand text.

What is refraction?

Refraction is the bending of light as it passes from one transparent substance to another. This occurs because light travels at different speeds in different mediums. When light enters a medium at an angle, the change in speed causes the direction of the light to change. The amount of bending depends on the angle at which the light enters the new medium and on the properties of the medium.

Law of refraction

The behaviour of light during refraction is described by Snell's law. This law helps us predict the angle at which light will bend when entering another medium. Snell's law is expressed by the formula:

n1 * sin(θ1) = n2 * sin(θ2)

In this formula, n1 and n2 are the refractive indices of the first and second medium, while θ1 and θ2 are the angles of incidence and refraction, respectively. The refractive index is a measure of how much a material can bend light.

Visual example 1: Refraction in a glass of water

θ1 θ2 Air Water

Imagine a beam of light being cast into a glass of water at an angle. As the light hits the surface of the water, it bends because it is moving from air (a less dense medium) to water (a more dense medium).

Factors affecting refraction

Density of mediums

The density of the media involved plays an important role. When light travels from a less dense medium to a more dense medium, it bends towards the normal. Conversely, when traveling from a denser medium to a less dense medium, light bends away from the normal.

Wavelength of light

The wavelength of light can also affect how much it refracts. Different colours of light have different wavelengths. For example, red light has a longer wavelength than blue light, which means that red light bends less than blue light when passing through the same medium.

Visual example 2: Prisms and light dispersion

Prisms are excellent for demonstrating the dispersion of light, which is the splitting of light into different colors. When white light enters the prism, each color is refracted by a different amount, creating a spectrum. This is why we can see a rainbow of colors emerging from a prism.

Real-world applications of refraction

Optical instruments

Refraction is essential in designing lenses for eyeglasses, cameras, microscopes and telescopes. These instruments use lenses to bend and focus light, allowing us to see better or magnify small objects.

Mirage

During summer days, you must have seen a water-like sight on the roads. This is a mirage and it is caused by the refraction of light in layers of air at different temperatures.

Common misconceptions

A common misconception about refraction is that it is confused with reflection. While both involve light traveling in different directions, reflection occurs when light bounces back into the same medium, while refraction involves light bending into a different medium.

Visual example 3: Lens focus and refraction

A convex lens can converge light rays and focus them into a single point. This ability to refract light makes the lens important in devices such as magnifying glasses and cameras.

Conclusion

Refraction is an important concept in light and optics, helping us understand how light behaves when it passes through different materials. Whether it's creating beautiful rainbows, allowing us to see clearly through glasses, or helping us capture stunning photographs, the bending of light is an essential phenomenon in our daily lives.


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Refraction of light

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