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 ↓


Characteristics of sound waves – frequency, amplitude, wavelength


Sound is all around us, from the chirping birds in the trees to the hum of cars in traffic. In physics, sound is considered a type of wave that travels through a medium, usually air, and reaches our ears. To understand how sound travels and behaves, we need to study the characteristics of sound waves, such as frequency, amplitude, and wavelength.

What is a sound wave?

A sound wave is a mechanical wave produced by the back-and-forth vibration of the particles of the medium through which the sound wave is traveling. These vibrations create regions of high pressure (called compression) and low pressure (called rarefaction) in the air, which propagate outward as sound waves.

Pressure Sparring

Understanding frequency

Frequency refers to the number of complete waves or cycles that pass a particular point in one second. It is usually measured in hertz (Hz), where one hertz equals one cycle per second. The frequency of a sound wave determines its pitch. Higher frequency means higher pitch, and lower frequency means lower pitch.

For example, a sound wave with a frequency of 440 Hz would be perceived as the musical note "A" above middle C. This frequency is often used as the standard tuning pitch for musical instruments.

High frequency

What is dimension?

Amplitude is the height of the wave above its average (resting) position. It represents the energy of the wave. In sound waves, amplitude is associated with the volume or loudness of the sound. Higher amplitude means louder sound, while lower amplitude means softer sound.

Imagine two people shouting. If one person shouts louder than the other, the amplitude of their sound waves is larger. This is because a louder sound has more energy and therefore causes more vibrations in the air.

Big dimension

Explanation of wavelength

Wavelength is the distance between two consecutive points that are in the same phase on a wave, such as from one peak to the next or from one trough to the next. Wavelength is usually measured in meters (m). In sound waves, wavelength is inversely proportional to frequency. This means that as the frequency increases, the wavelength decreases.

Mathematically, the relationship between the speed of sound ( v ), its frequency ( f ) and its wavelength ( λ ) is given by the formula:

v = f × λ

where v is the speed of sound, f is the frequency, and λ is the wavelength.

Wavelength

How frequency, amplitude, and wavelength are related

Frequency, amplitude and wavelength are interrelated properties of sound waves. A sound wave can be high-pitched (high frequency), loud (high amplitude) and have a short wavelength. Conversely, a sound wave can be low-pitched (low frequency), soft (low amplitude) and have a long wavelength.

To understand these relationships, imagine a guitar string. When played lightly, the string vibrates with a small amplitude, producing a soft sound. If played hard, the string vibrates with a large amplitude, resulting in a loud sound. If the tension of the string is increased, the frequency of vibration increases, producing a high-pitched sound with a shorter wavelength.

The speed at which sound travels through a medium also affects these characteristics. In air, the speed of sound is about 343 meters per second at room temperature. This speed can vary depending on factors such as temperature, humidity, and air pressure.

Everyday examples of sound waves

Understanding the characteristics of sound waves can help us understand the world around us. Here are some everyday examples:

  • Musical instruments: The pitch of the sound produced by a musical instrument depends on the frequency of the sound waves it produces. Higher tension or shorter length of the string or air column usually produces higher frequency sounds.
  • Volume control: Adjusting the volume on a device increases or decreases the amplitude of the sound waves it emits. Higher volume means greater amplitude and more energy.
  • Ultrasound: Ultrasound machines use high-frequency sound waves to take pictures of the inside of the human body. These sound waves have a short wavelength and can detect small structures.

Conclusion

Understanding the properties of sound waves is essential to understanding how sound travels and behaves. By exploring frequency, amplitude, and wavelength, we gain information about the properties of sound, allowing us to appreciate the variety of sounds in our world. These fundamental principles provide the basis for more complex studies in physics and engineering.


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Production and propagation of sound
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Speed of sound in different mediums

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Characteristics of sound waves – frequency, amplitude, wavelength

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