Grade 7
  1. Introduction to Physics  1.1. Definition and scope of physics  1.2. Importance of Physics in Daily Life and Technology  1.3. Scientific method and its applications in physics  1.4. Measurement and Experiments in Physics  1.5. Branches of Physics and their Applications  1.6. Relation of physics with other sciences
  2. Measurement and units  2.1. Fundamental and derived quantities  2.2. SI units and unit conversions  2.3. Length measuring instruments and tools used  2.4. Measuring the difference between mass and weight  2.5. Measuring time with accuracy  2.6. Measuring the Volume of Regular and Irregular Objects  2.7. Measuring Temperature and Temperature Scales  2.8. Accuracy, Precision, and Significant Figures  2.9. Errors in Measurement and How to Reduce Them  2.10. Estimates and approximations in scientific calculations  2.11. Standard form and order of magnitude
  3. Speed and Force  3.1. Introduction to motion and rest  3.2. Types of motion - uniform and non-uniform  3.3. Scalars and vectors in motion  3.4. Speed, Velocity, and Acceleration  3.5. Distance-time and velocity-time graphs  3.6. Newton's first law of motion (law of inertia)  3.7. Newton's second law of motion (force and acceleration)  3.8. newton's third law of motion  3.9. Types of forces - contact and non-contact forces  3.10. Effect of forces on motion  3.11. Friction – types, effects and applications  3.12. Gravity, free fall and gravitational acceleration  3.13. Circular motion and centripetal force  3.14. Application of Newton's laws in real life
  4. Energy, Work and Power  4.1. Definition and forms of energy  4.2. Potential and Kinetic Energy  4.3. Law of conservation of energy  4.4. Energy transformations in everyday life  4.5. Work done by force and its calculation  4.6. Power - Definition and Calculation  4.7. Simple Machines and Mechanical Advantage  4.8. Efficiency and energy losses of machines  4.9. Renewable and non-renewable energy sources
  5. Heat and temperature  5.1. Difference Between Heat and Temperature  5.2. Thermometer and temperature scale (Celsius, Kelvin, Fahrenheit)  5.3. Expansion and contraction of solids, liquids and gases  5.4. Heat transfer methods – conduction, convection and radiation  5.5. good and bad conductors of heat  5.6. Applications of heat transfer in daily life  5.7. Specific heat capacity and its applications  5.8. Latent heat and change of state  5.9. Thermal equilibrium and heat exchange  5.10. effect of heat on matter
  6. Lighting and Optics  6.1. Nature and properties of light  6.2. Reflection of light and laws of reflection  6.3. Image formation by plane and curved mirrors  6.4. Refraction of light and the laws of refraction  6.5. Lenses – convex and concave, image formation  6.6. Optical instruments – microscope, telescope, camera  6.7. Dispersion of light and formation of spectrum  6.8. Human eye, vision defects and their correction  6.9. Applications of optics in daily life  6.10. Total internal reflection and its applications
  7. Sound and waves  7.1. Nature and properties of waves  7.2. Production and propagation of sound  7.3. Characteristics of sound waves – frequency, amplitude, wavelength  7.4. Speed of sound in different mediums  7.5. Reflection of sound – echo and reverberation  7.6. Ultrasound and its applications  7.7. Doppler effect in sound waves  7.8. Noise pollution and its effects  7.9. Applications of sound in medicine and industry
  8. Electricity and Magnetism  8.1. Electric charge and static electricity  8.2. Electrical conductors and insulators  8.3. Electric current, voltage and resistance  8.4. Ohm's law and its applications  8.5. Electrical Circuits - Series and Parallel Circuits  8.6. Electric power and energy consumption  8.7. Safety precautions in the use of electricity  8.8. Properties of magnets and magnetic fields  8.9. Electromagnets - How They Work and Their Uses  8.10. Relation between electricity and magnetism (electromagnetic induction)  8.11. Applications of electromagnetism in technology  8.12. Earth's magnetic field and its effects
  9. Matter and its properties  9.1. Classification of matter- solid, liquid and gas  9.2. Properties of different states of matter  9.3. Kinetic theory of matter  9.4. Changes in the state of matter and their causes  9.5. Expansion and contraction of substances  9.6. Density and its calculation  9.7. Pressure in solids, liquids and gases  9.8. Atmospheric pressure and its effects  9.9. Applications of pressure in daily life  9.10. Buoyancy and Archimedes' principle
  10. Space Science and Solar System  10.1. Introduction to Astronomy  10.2. Solar System - Planets and their Characteristics  10.3. Sun - structure and energy production  10.4. Moon - phases and its effect on Earth  10.5. Rotation and revolution of the earth  10.6. Solar and lunar eclipses  10.7. Gravity in space and its role in orbits  10.8. Artificial satellites and their uses  10.9. Space exploration and modern discoveries  10.10. Asteroids, comets and meteors  10.11. Life beyond Earth - Possibilities and Theories
  11. Environmental Physics  11.1. Impact of physics on environmental science  11.2. Renewable and non-renewable energy sources  11.3. Energy conservation and efficiency  11.4. Climate change and its effects on Earth  11.5. Air, water and soil pollution – causes and effects  11.6. Greenhouse effect and global warming  11.7. Sustainable development and environmental protection  11.8. Role of Physics in Weather and Climate Studies

Grade 7 → Lighting and Optics ↓


Nature and properties of light


Light is a fascinating phenomenon that has puzzled and intrigued humans for centuries. It is a form of energy that allows us to see the world around us. In this lesson, we will explore the basic nature and properties of light, which are fundamental topics in the study of optics.

What is light?

Light is a type of energy known as electromagnetic radiation. It is made up of tiny particles called photons, which travel in waves. The range of different wavelengths and frequencies of light is called the electromagnetic spectrum, and visible light is just a small part of this spectrum.

Wave like light

Light behaves like a wave. This means that it has properties such as wavelength and frequency:

  • Wavelength: The distance between two successive crests (or troughs) of a wave.
  • Frequency: The number of waves that pass a point in one second. It is measured in Hertz (Hz).

The speed of light in a vacuum is approximately 299,792,458 meters per second, which is typically 300,000 km/s.

Light as a particle

Light can behave like a wave, but it can also behave like a particle. The particle nature of light is evident when it interacts with matter. For example, when light strikes a metal surface under certain conditions, it can release electrons from the metal. This phenomenon is called the photoelectric effect. The particle nature of light is used in technologies such as solar panels, where light energy is used to generate electricity.

Properties of light

1. Linear expansion

Light travels in straight lines. This is known as rectilinear propagation. We can observe this property by looking at shadows. When light is blocked by an object, a shadow of the same size as the object is formed, which shows that light travels in a straight path.

2. Reflection of light

When light hits a surface, it bounces back. This is called reflection. The law of reflection states that the angle of incidence is equal to the angle of reflection. This is why we can see ourselves in a mirror.

incident ray Reflected ray

3. Refraction of light

When light passes from one medium to another (e.g., from air to water), its speed changes and it bends. This bending is called refraction. An example of refraction is a straw placed in a glass of water appearing bent on the surface.

4. Scattering of light

Dispersion occurs when light is split into its component colors. White light, such as sunlight, is made up of all the colors of the rainbow. When it passes through a prism, it separates into individual colors. This is why prisms can create the rainbow effect.

5. Diffraction and interference

Diffraction is the bending of light around obstacles. It occurs when a wave of light hits an obstacle or a hole that is close in size to its wavelength, causing the light to scatter. Interference occurs when two or more waves overlap, creating a new pattern. These are more complex behaviors exhibited by light.

Wave Pattern

How do we see colors

The colors we see depend on how different objects interact with light. An object appears a certain color because it reflects that particular color of light and absorbs other colors. For example, a leaf appears green because it absorbs all other colors and reflects green light.

Polarization of light

Polarization refers to the direction in which a light wave oscillates. Normally, light waves vibrate in many directions, but polarized light waves vibrate in only one direction. Sunglasses use this property to reduce glare from surfaces such as water and roads by blocking certain directions of light waves.

Light in the natural world

Light plays an important role in the natural world. It is vital for photosynthesis in plants, helping them convert sunlight into energy. The changing angle of sunlight throughout the day helps regulate biological clocks in living organisms. The light coming from the sun is responsible for the beautiful colors we see during sunrise and sunset.

Conclusion

Understanding light and its properties gives us insight into the workings of the natural world. The unique properties of light – such as its ability to reflect, refract and scatter – give rise to the rich variety of visual phenomena that we encounter every day. The study of light not only explains how we see but also helps us develop technologies for communication, medicine and entertainment that improve our lives.


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