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


The study of light and its interaction with various substances and objects is known as optics. Optics is an important part of physics that helps us understand how we see things with our eyes and how various instruments like spectacles, cameras and microscopes work.

What is light?

Light is a form of energy that travels in waves. It is made up of photons, which are tiny packets of energy. Unlike sound, which needs a medium such as air or water to travel, light can travel through empty space.

Imagine the Sun. The Sun is a giant ball of gases that emits light. This light travels through the vacuum of space to reach the Earth, and takes about eight minutes to do so. Without light, we would not be able to see anything.

Properties of light

  • Speed: Light travels incredibly fast in a vacuum, at about 299,792 km/s
  • Wavelength: The distance between the two peaks of a light wave. Different colors of light have different wavelengths.
  • Frequency: The number of waves that pass a point in one second. Frequency is measured in Hertz (Hz).

There is a simple relationship between the speed of light, its wavelength (λ) and its frequency (f), as follows:

c = λ * f

where c is the speed of light.

Nature of light

Light exhibits both particle and wave characteristics, a concept known as wave-particle duality. Sometimes light behaves like a wave, as seen in interference patterns, and other times it acts like a particle, for example, when it collides with a surface.

Reflection of light

Reflection occurs when light bounces off a surface. A clear example of reflection is seeing your image in a mirror. Mirrors have a smooth and shiny surface that reflects almost all the incident light.

When light falls on a mirror, it follows the law of reflection, which states:

  • The angle of incidence (the angle at which the incoming light hits the surface) is equal to the angle of reflection (the angle at which it bounces back).
incident ray Reflected ray General

Refraction of light

Refraction is the bending of light as it passes from one medium to another medium with different densities. This is why a straw in a glass of water appears bent or broken on the surface of the water.

This bending is caused by a change in the speed of light as it enters a new medium. The amount of bending depends on the refractive index of the mediums involved. Snell's law helps describe this behavior:

n1 * sin(θ1) = n2 * sin(θ2)

Here, n1 and n2 are the refractive indices of the respective media, while θ1 and θ2 are the angles of incidence and refraction, respectively.

incident ray Refracted ray

Dispersion of light

Dispersion of light occurs when light is separated into its component colours. This happens because different colours (wavelengths) of light bend differently when passing through a medium such as glass.

A common example of dispersion is a rainbow. After it rains, water droplets in the air act like tiny prisms, splitting sunlight into the colors of the rainbow.

Lenses and their types

Lenses are pieces of glass or other transparent materials that refract light to form an image. There are two main types:

  • Convex lens: Thick in the middle and thin at the edges, focuses light rays to a point.
  • Concave lens: Thin in the middle and thick at the edges, scatters light rays outward.
convex lens Concave Lens

Vision and optics

The human eye is a complex organ that uses light to form images. When light enters the eye, it passes through the cornea and lens, and is focused on the retina. The retina then sends signals to the brain, which interprets them as visual images.

Sometimes, the lenses in our eyes fail to focus light correctly, causing vision problems. Glasses and contact lenses are designed to correct these problems by adjusting the way light enters the eyes.

Practical applications of light

Optics is not just theoretical; it has many practical applications. Here are some examples:

  • Camera: Use the lens to focus light and take a picture.
  • Telescope: Magnifies distant objects by gathering and focusing light.
  • Microscope: Makes small objects appear larger by using a lens to focus light.

Understanding the basic principles of light and optics helps us harness its power for a variety of applications, from improving our vision to capturing beautiful moments with cameras. By exploring light and its behavior through reflection, refraction, and dispersion, we gain insight into both our natural environment and technological advancements.


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Lighting and Optics

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