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 → Sound and waves ↓


Production and propagation of sound


Sound is an incredible phenomenon that we experience every day. Whether it is music, conversations or the chirping of birds, it enriches our lives. But what exactly is sound, and how does it travel through the air to reach our ears? It can be interesting to understand the production and propagation of sound. Let us look at this fascinating world of sound in a simple and detailed manner.

The basics of sound

Sound is a type of energy that travels through air (or other mediums) as waves. It is created by the vibrations of objects. Consider a simple example: When you strike a tuning fork, it vibrates. These vibrations disturb the surrounding air molecules. This movement creates sound waves that travel to your ears, allowing you to hear sound.

What is vibration?

Vibration is a rapid back-and-forth motion. When an object vibrates, it pushes against nearby air molecules. These molecules, in turn, push against others, creating a wave-like effect. Vibrations in an object in this way transfer energy to the surrounding air, creating a sound wave.

// Visual Representation of Vibration Object Vibration: |---|---|---| Vibrating Object: |---|---|---| up down up up down up

Understanding sound waves

A sound wave is a series of compressions and rarefactions. It can be visualised as a wave with crests and troughs.

Compression and rarefaction

- Compression: These are areas where air molecules gather together.

- Rarefaction: These are regions where the air molecules are spread out.

// Visual Example of a Sound Wave Sound Wave: |-----| |-----| |-----| |-----| Compressions: Dense Regions Rarefactions: Sparse Regions

Transmission of sound

Propagation refers to the way sound waves travel through a medium. Sound can travel through gases, liquids, and solids. The way sound propagates depends on the properties of the medium.

How does sound travel?

Sound needs a medium to travel because it depends on the motion of particles to propagate. Without particles, as in a vacuum, there would be no sound. This is why space is quiet even though it is full of activity.

Example: Consider talking underwater while swimming. The sound of your voice changes because water is a different medium than air, which is the normal medium for sound transmission on Earth.

Medium and speed of sound

  • Air: The speed of sound at room temperature is about 343 meters per second.
  • Water: The speed of sound in water is about 1482 meters per second.
  • Steel: In solid materials like steel, sound can travel even faster, about 5960 meters per second.

This difference in speed is due to the arrangement of particles in different media. In solids, the particles are closer together, which makes the transmission of sound faster than in liquids and gases.

Frequency and amplitude

Sound waves are characterized by two main properties: frequency and amplitude. These properties determine the intensity and loudness of sound.

Frequency

Frequency refers to how many times a sound wave cycles in a second. It is measured in Hertz (Hz).

  • Higher frequency: More cycles per second correspond to a higher pitch. For example, a whistle has a higher frequency.
  • Low frequency: Fewer cycles per second correspond to a lower pitch. For example, a bass drum has a low frequency.

Amplitude

Amplitude refers to the height of the sound wave. It relates to how loud or slow the sound is.

  • Bigger amplitude: Louder sound.
  • Small amplitude: Soft sound.
// Visual Example of Frequency and Amplitude High Frequency: ////// Low Frequency: /  /  Large Amplitude: ------ Small Amplitude: ----

Applications of sound

Sound has countless uses in our lives and technology. Let's take a look at some practical uses.

Communications

Sound is fundamental in human communication. From talking face-to-face to singing, sound allows us to express emotions and thoughts.

Technology

  • Sonar: Used in ships to detect underwater objects by sending out sound waves and measuring the time taken for them to return.
  • Medical ultrasonography: Used to make images of the inside of the body.

Conclusion

Sound is a remarkable form of energy that affects our daily lives in many ways. By understanding the fundamental concepts of how sound is produced and transmitted, we gain a deeper understanding and ability to harness its power for many practical applications. From music to technology, the world of sound continues to be interesting and invites exploration.


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Nature and properties of waves
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Characteristics of sound waves – frequency, amplitude, wavelength

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Production and propagation of sound

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