Grade 10
  1. Mechanics  1.1. Dynamics  1.1.1. Motion in one dimension  1.1.2. Motion in two dimensions  1.1.3. Displacement and Distance  1.1.4. Speed and Velocity  1.1.5. Acceleration  1.1.6. Graphical representation of motion  1.1.7. Equations of motion  1.1.8. Free fall and acceleration due to gravity  1.1.9. Projectile motion  1.1.10. Relative speed  1.2. Dynamics  1.2.1. Newton's Laws of Motion  1.2.2. Inertia and mass  1.2.3. Force and its types  1.2.4. action and reaction force  1.2.5. Friction and its effects  1.2.6. Coefficient of friction  1.2.7. Circular motion  1.2.8. Centripetal force and centripetal acceleration  1.2.9. Momentum and Impulse  1.2.10. Conservation of momentum  1.2.11. Newton's third law and applications  1.3. Work, Energy and Power  1.3.1. Work done by the force  1.3.2. Work–energy theorem  1.3.3. Kinetic energy  1.3.4. Potential energy  1.3.5. Mechanical energy  1.3.6. Energy Conservation  1.3.7. Power and efficiency  1.3.8. Renewable and non-renewable energy sources  1.4. Gravitational force  1.4.1. Newton's law of universal gravitation  1.4.2. Gravitational field and field strength  1.4.3. Acceleration due to gravity on different planets  1.4.4. Kepler's laws of planetary motion  1.4.5. Orbits and satellites  1.4.6. Weight and apparent weight  1.4.7. Gravitational potential energy
  2. Properties of matter  2.1. States of matter  2.1.1. Solid, liquid and gas  2.1.2. Molecular structure of matter  2.1.3. Intermolecular forces  2.1.4. Plasma and Bose–Einstein condensate  2.2. Pressure  2.2.1. Definition of Pressure  2.2.2. Pressure in liquids  2.2.3. Atmospheric pressure  2.2.4. Pascal's principle  2.2.5. Archimedes' Principle and Buoyancy  2.2.6. Surface tension and capillarity  2.3. Elasticity  2.3.1. Hooke's law  2.3.2. Stress and strain  2.3.3. Elastic Limit and Modulus of Elasticity  2.3.4. Applications of Elasticity
  3. Thermal physics  3.1. heat and temperature  3.1.1. Difference Between Heat and Temperature  3.1.2. Temperature scale  3.1.3. Thermal expansion  3.1.4. Thermal equilibrium  3.2. Heat transfer  3.2.1. Conductivity  3.2.2. Convection  3.2.3. Radiation  3.2.4. Insulation and its applications  3.3. Thermal properties of matter  3.3.1. Specific heat capacity  3.3.2. Latent heat and phase change  3.3.3. Boiling and Melting Point  3.3.4. Heat engines and refrigeration  3.4. Laws of Thermodynamics  3.4.1. Zeroth law of thermodynamics  3.4.2. First law of thermodynamics  3.4.3. Second law of thermodynamics  3.4.4. Carnot cycle
  4. Waves and optics  4.1. Nature and properties of waves  4.1.1. Types of waves in nature and properties of waves  4.1.2. Transverse and longitudinal waves  4.1.3. Wave parameters  4.1.4. Reflection and refraction of waves  4.1.5. Superposition and Interference  4.1.6. Standing Waves and Resonance  4.1.7. Doppler effect  4.2. Sound waves  4.2.1. Characteristics of sound waves  4.2.2. Speed of sound in different mediums  4.2.3. Applications of sound waves  4.2.4. Ultrasound and its uses  4.3. Light Waves and Optics  4.3.1. Nature of light  4.3.2. Reflection of light  4.3.3. Laws of reflection  4.3.4. Mirrors and Image Formation  4.3.5. Refraction of light  4.3.6. Snell's Law  4.3.7. Lenses and Image Formation  4.3.8. Total internal reflection and critical angle  4.3.9. Optical fibre  4.4. Optical Instruments  4.4.1. Microscope  4.4.2. Telescope  4.4.3. Human eye and vision defects  4.4.4. Camera and its working principle
  5. Electricity and Magnetism  5.1. Electrostatics  5.1.1. Electric charge and its properties  5.1.2. Conductors and Insulators  5.1.3. Coulomb's law  5.1.4. Electric field and field lines  5.1.5. Electric potential and potential difference  5.1.6. Capacitors and Capacitance  5.2. Current Electricity  5.2.1. Electric current and its measurement  5.2.2. Ohm's law  5.2.3. Resistance and resistivity  5.2.4. Series and Parallel Circuits  5.2.5. Electric power and energy  5.2.6. Kirchhoff's Laws  5.3. Magnetism and Electromagnetism  5.3.1. Magnetic field and field lines  5.3.2. Magnetic effects of electric current  5.3.3. Electromagnetic induction  5.3.4. Faraday's laws of electromagnetic induction  5.3.5. Transformers and Applications  5.3.6. AC and DC current
  6. Modern Physics  6.1. Nuclear physics  6.1.1. Structure of the atom  6.1.2. Bohr's atomic model  6.1.3. Electron Energy Levels  6.1.4. X-rays and applications  6.2. Radioactivity  6.2.1. Types of radiation  6.2.2. Half-life and radioactive decay  6.2.3. Nuclear reactions and applications  6.2.4. Fission and Fusion  6.3. Quantum physics  6.3.1. Wave–particle duality  6.3.2. Photoelectric effect  6.3.3. Energy quantization  6.3.4. Heisenberg's uncertainty principle
  7. Electronics and Communication  7.1. Semiconductors  7.1.1. Conductors, Insulators and Semiconductors  7.1.2. Diodes and their applications  7.1.3. Transistors and Logic Gates  7.1.4. LEDs and photodiodes  7.2. Communication Systems  7.2.1. Basics of communication  7.2.2. Analog and digital signals  7.2.3. Wireless and optical fibre communication  7.2.4. Radio Waves and Modulation

Grade 10 → Waves and optics → Sound waves ↓


Speed of sound in different mediums


Sound is a type of wave known as a mechanical wave. Mechanical waves require a medium, such as air, water, or a solid, to travel. An interesting aspect of sound waves is that the speed of sound varies considerably in different mediums. In this article, we will explore the factors that affect the speed of sound and how it travels through different substances.

What is sound?

Sound is a wave that is created by vibrating objects and travels through a medium from one place to another. When an object vibrates, it causes the surrounding medium to vibrate. In the case of air, the vibrating object compresses and rarefactions the air molecules in the form of sound waves that propagate outward.

Basic properties of sound waves

To understand how sound travels at different speeds, we must first consider the basic properties of sound waves. Sound waves have frequency, wavelength, amplitude, and velocity. The speed at which sound travels is known as the speed of sound.

Frequency and wavelength

The frequency of a sound wave is the number of vibrations or cycles per second and is measured in hertz (Hz). The wavelength is the distance between successive compressions or rarefactions. The relationship between speed (v), frequency (f), and wavelength (λ) is given by the formula:

v = f * λ

Dimensions

The amplitude of a sound wave determines its loudness. Higher amplitude means a louder sound, but amplitude does not affect the speed of sound.

Velocity

The velocity of sound depends on the medium through which it travels. Different mediums have different properties that affect the speed of sound.

Factors affecting the speed of sound

Several factors affect how fast sound travels through a medium:

1. Medium type

The type of medium plays an important role in determining the speed of sound. Sound can travel at different speeds through gases, liquids, and solids. The general rule is that sound travels fastest in solids, slower in liquids, and slowest in gases.

2. Temperature

The speed of sound is affected by the temperature of the medium. In general, as the temperature increases, the speed of sound also increases. This is because higher temperatures force the molecules in a gas to move faster and collide more often, speeding up the propagation of the sound wave.

3. Density

The density of the medium also affects the speed of sound. In most cases, the denser the medium, the faster the speed of sound. This is contrary to popular belief, but it makes sense when considering molecular interactions.

4. Elasticity

Elasticity refers to the ability of a material to return to its original shape after being deformed. Materials with high elasticity allow sound to travel faster because they transfer energy between particles efficiently.

Speed of sound in different mediums

To explain how sound travels at different speeds, let's examine several common mediums:

Sound in the air

Air is a common medium for sound to travel through. At room temperature (about 20°C or 68°F), the speed of sound in air is about 343 meters per second (m/s).

Speed of sound in air ≈ 343 m/s

Factors such as humidity and pressure can also affect the speed of sound in air, but temperature is the most important factor.

For example, in summer the air is hotter, so sound travels faster. In winter, sound travels slower because the air is colder.

Sound in the water

Water is a much denser medium than air, which is why sound generally travels faster. The speed of sound in water is about 1482 meters per second (m/s).

Speed of sound in water ≈ 1482 m/s

Sound travels about 4.3 times faster in water than in air. This is why marine mammals such as dolphins use sound for communication and navigation in water.

Sound in solids

Solids are the densest state of matter, and sound travels faster through them due to their high elasticity. For example, sound travels at a speed of about 5000 m/s in steel.

Speed of sound in steel ≈ 5000 m/s

Other common solids include wood, glass, and metal, each of which has its own speed of sound. Generally, metals have a higher speed of sound than organic materials such as wood.

Sound in space

Space is a vacuum, which means there is no medium for sound waves to travel through. In the emptiness of space, there are no particles to vibrate and carry sound waves, so sound cannot be transmitted.

Visual example of the speed of sound

Consider the following illustration showing sound waves propagating through different mediums:

Wind (343 m/s) Water (1482 m/s) Steel (5000 m/s) Air Water steel

Practical examples of sound in different media

Let us understand how the speed of sound varies in different mediums through some practical examples:

Echoes in the valleys

A common phenomenon that many people experience is echo in valleys or large empty spaces. When you shout, sound waves travel through the air, hit a solid surface such as a valley wall, and come back to your ears. The delay between shouting and the echo can help estimate the distance to the object reflecting the sound.

Sonar in water

Sonar (an abbreviation for sound navigation and ranging) uses sound waves to detect underwater objects. Submarines and ships emit sonar pulses that travel through the water. When these pulses strike an object, they are reflected back, allowing the distance to the object to be calculated based on the time it takes for the echo to return, using the known speed of sound in water.

Railway tracks

Did you know that you can often hear the sound of a train through the vibrations of the train tracks before you hear it in the air? That's because sound travels faster through steel tracks than it does through air. By (carefully) placing your ear to the tracks, you can hear the vibrations before you see the train.

Conclusion

Understanding the speed of sound in different mediums is an essential part of physics and helps explain a variety of natural phenomena and technologies. The speed of sound is affected by the properties of the medium, such as density, elasticity, and temperature. Sound travels fastest in solids, slowest in liquids, and slowest in gases. This knowledge is important for applications in communications, engineering, monitoring, and music.


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Characteristics of sound waves
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Speed of sound in different mediums

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