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 → Waves and sound → Waves and their types ↓


Longitudinal and Transverse Waves


Waves are an integral part of our daily experience. From the sound of music to the light we see, understanding the nature of waves helps us understand a variety of phenomena. In physics, waves are primarily classified into two types: longitudinal and transverse waves. In this article, we will explore these wave forms, their properties, characteristics, and examples using simple language and plenty of examples.

What are waves?

A wave is a disturbance that travels through a medium, transferring energy from one point to another without moving matter. The medium through which the wave travels may be solid, liquid, gas or, in some cases, vacuum (such as light waves in space). Waves can be caused by a variety of factors such as vibrations, changes in pressure or even electromagnetic interactions.

Understanding Wave Terminology

Before diving into longitudinal and transverse waves, it is important to understand some basic terms:

  • Crest: The highest point of a wave.
  • Trough: The lowest point of the wave.
  • Wavelength (λ): The distance between two successive crests or troughs.
  • Amplitude: The maximum displacement of points on a wave, which indicates the energy of the wave.
  • Frequency (f): The number of waves that pass a point in a given period of time, usually measured in hertz (Hz).
  • Wave speed (v): The speed at which a wave travels through a medium.
  • Period (T): The time it takes for one complete wave to pass a point, which is the inverse of the frequency: T = 1/f.

Longitudinal waves

Longitudinal waves are waves in which the displacement of the medium is in the direction of the wave itself. They are marked by regions of compression and rarefaction. To understand longitudinal waves, consider the following example:

Sound waves

Think of a tuning fork. When you strike the tuning fork, it vibrates and creates sound waves in the air. These sound waves are longitudinal waves. When the vibrating tuning fork compresses air particles, these particles push against each other, creating an area of high pressure known as compression. As the tuning fork moves backward, it pushes air particles apart, creating an area of low pressure known as rarefaction. These compressions and rarefactions travel through the air as a longitudinal wave, eventually reaching your ear.

Pressure sparring Pressure

The above figure shows a longitudinal wave in red circles, where distance between the circles is less on 'compression' and more on 'rarefaction'.

Properties of Longitudinal Waves

  • Travel in the direction of vibration of the medium.
  • It consists of alternating compression and rarefaction.
  • Can travel through solids, liquids, and gases.

Mathematics of longitudinal waves

The wave speed for longitudinal waves can be calculated using the formula:

v = f × λ

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

Example: Earthquake P-waves

Seismic waves travel through the Earth's crust. They are classified into two main types: primary waves (P-waves) and secondary waves (S-waves). P-waves are longitudinal waves that compress and expand the material they pass through, causing them to travel faster than S-waves. Seismographs detect P-waves to evaluate the location and size of an earthquake.

Transverse waves

Unlike longitudinal waves, transverse waves are waves where the displacement of the medium is perpendicular to the direction of the wave. These waves are characterized by crests and troughs. To understand transverse waves, consider the following example:

Waves on a string

If you tie a rope to a wall and shake its free end up and down, you will create waves that move along the rope. These waves are transverse waves. Here, the rope rises up to form a peak, then falls down to form a trough, while the wave itself moves horizontally toward the wall.

Crest Trough

The above figure shows a transverse wave on a string, where the peaks are crests and the valleys are troughs.

Properties of Transverse Waves

  • Travel perpendicular to the direction of vibration of the medium.
  • Made up of peaks and troughs.
  • Can travel through solids, but usually not through gases or liquids.

Mathematics of Transverse Waves

Similarly, the wave speed of transverse waves is determined by:

v = f × λ

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

Example: Electromagnetic waves

Light waves and other forms of electromagnetic radiation (such as radio waves, microwaves, X-rays) are examples of transverse waves that travel without requiring a medium. The electric and magnetic fields in these waves oscillate perpendicular to the direction in which the wave is traveling.

Comparative Summary

In conclusion, both longitudinal and transverse waves are fundamental to the nature of wave phenomena, but differ in the way they accelerate the particles of the medium:

  • Longitudinal Waves:
    • The displacement is parallel to the wave direction.
    • Demonstrate compression and rarefaction.
    • Examples include sound waves and seismic P-waves.
  • Transverse Waves:
    • The displacement is perpendicular to the wave direction.
    • Demonstrate peaks and troughs.
    • Examples include waves on a string and electromagnetic waves.

Conclusion

Understanding longitudinal and transverse waves gives us insight into a variety of natural and technological processes. From the sound we hear to the light we see, waves play a vital role in the transfer of energy in the universe. By studying both types of waves, we are better equipped to appreciate and use the dynamic world of wave phenomena.


Grade 9 → 4.1.2


U
username
0%
completed in Grade 9

← Prev (4.1.1)
Mechanical and electromagnetic waves
Next (4.1.3) →
Properties of Waves

Comments 



Longitudinal and Transverse Waves

https://www.physicsflow.com/g9/4.1.2?pfal=en