Types of Waves

Wave is a disturbance in some substance that propagates from one place to another through the medium or without a medium. There are different types of waves such as Mechanical, Electromagnetic or Matter. Waves have the ability to travel through solids, liquids, and gases. Waves come in various forms, such as transverse, longitudinal, or neither. While Waves transport energy and momentum, they don’t carry any mass. In this article, we will understand the definition of Wave and various Types of Waves in detail along with their Properties and uses.

What are Waves?

Wave is the transmission of energy and momentum, with or without a material medium, from one location to another without physically moving the particles of the medium. The disturbance in the Wave travels through the medium due to repeated, rhythmic oscillations of the medium’s particles around their average position. The energy can travel through various forms, like elastic deformation of a medium particle, changes in pressure, or variations in electric and magnetic field intensity. A practical example is our reliance on waves for wireless communication. Our voice, converted into an electrical signal by the phone, travels through either copper wires or antennas in wireless communication. The entire process of transmitting a signal from the sender to the receiver occurs in a waveform.

Wave Parameters

There are various parameters related to waves some of these parameters are:

Wavelength: The Wavelength, denoted as λ, marks the distance between any two successive crests or troughs of a wave. This length is determined by the Wave’s velocity (ν) and Frequency (f), as given by the formula λ=ν/f.

Amplitude: Amplitude (A), denoted as A, representing the wave’s energy, is the peak displacement from the neutral position. A higher amplitude signifies greater energy.

Time period (T): It measures the time for two successive crests (one wavelength) to pass a specific point. It’s expressed in seconds (s) and related to frequency (f) by the formula T=1/f.

Frequency (f): It quantifies the number of waves or oscillations passing a point in a given time, measured in Hertz (Hz).

Wave Velocity (v): It signifies the speed at which a specific part of the wave passes a point. In a medium, the Wave’s velocity remains constant, while particle velocity varies during vibration. The speed of a light wave in a vacuum is 3×108 m/s, and the relationship among velocity (v), frequency (f), and wavelength (λ) is defined by v = f×λ.

Types of Waves

There are mainly three Types of Waves:

• Mechanical Waves
• Electromagnetic Waves
• Matter Waves

Mechanical Waves

Mechanical Waves need a medium for their propagation, necessitating passage through a material. The particles of the medium, which remain constant, oscillating solely around their mean position, the waves themselves carry the energy forward. The transmission of these waves is fueled by the collision and energy exchange among molecules within the medium. Examples of mechanical waves are waves in a stretched string, sound waves, tsunami waves, and waves arising from the oscillation of a spring.

Types of Mechanical Waves

The Mechanical Wave further can be classified in two different types

• Transverse waves
• Longitudinal waves

Transverse Waves

Transverse Waves defined as vibrations where the medium’s particles oscillate at right angles to the wave’s motion. The pivotal point around which these particles oscillate is termed the mean position. The highest point in the wave is identified as the crest, while the lowest is the trough. Examples of transverse waves include waves on a string, oscillation of a spring, water waves, where the water moves up and down as the wave traverses the ocean. Light also exemplifies a Transverse Wave.

Longitudinal Wave

Longitudinal Waves are the waves in which the particles of the medium oscillate parallel to the direction of the wave’s motion. These Waves manifest as compressions and rarefactions, with compression occurring when particles draw closer and rarefaction when they move apart. Examples of Longitudinal Waves include sound waves, seismic P-type earthquake waves, and the oscillation of a spring. Water waves show a combination of both Longitudinal and Transverse motions.

Difference Between Transverse Waves And Longitudinal Waves

The difference between Transverse and Longitudinal wave is tabulated below:

Transverse Waves	Longitudinal Waves
Transverse waves moves perpendicular to the wave directions.	Longitudinal wave moves parallel to the wave directions.
It forms crests and troughs.	It travels by compressions and rarefactions.
It can travel through all the three mediums	It can propagate in solids, liquids and gases.
Transverse waves acts in two and three dimensions.	Longitudinal Waves acts only in one direction
It can be polarized.	It can not be polarized.
Light Waves and Water wave are the example of these waves.	Sound Wave and Seismic-P Wave are the example of this waves.

Electromagnetic Waves

Electromagnetic Waves are capable to flow through a vacuum, devoid of any need for a medium. Electromagnetic Waves propagates through space independently, without relying on a material medium. These Waves are a form of energy discharged and absorbed by charged particles. As these Electromagnetic radiations travels through space, they show a wave-like behaviour, characterized by the presence of both magnetic and electric fields. These fields are perpendicular to each other and oscillate perpendicular to the direction of the wave’s propagation.

Types of Electromagnetic Waves

In the increasing order of the wavelength the electromagnetic waves are:

• Gamma Rays: Gamma Rays have the wavelength less than 0.1A or 10-11 m . Used in radiation cancer therapy in medical field. It kills cancer cells. Its source is cosmic rays, radioactive substances.
• X- Rays: X- Rays have the wavelength 0.1A to 100A and used to see the inner body part. Its source is high energy electrons.
• Ultraviolet: It has the wavelength 100A to 4000A and used in fluorescent tubes. Its source is sunlight, arc lamp which is harmful for our skin.
• Visible light: Visible light has the wavelength 4000A to 8000A. Its source is sunlight and helps in seeing objects of different colors.
• Infrared: It has the wavelength 8000A to 10⁷A. Its source is lamp with thoriated filament. It is used in remote control light and CCTV light.
• Microwave: It has the wavelength 10⁷A to 10¹¹A. Its source is crystal oscillators and used in cooking, radar, speed gun telephone and other signals.
• Radio Waves: Radio Waves have the wavelength above 10¹¹A. It is used to broadcast the radio and television.

Matter Wave

The dual nature of matter was introduced by the French physicist De Broglie, who proposed that all matter possesses wave-like characteristics, termed as matter waves. According to this concept, when matter particles are in motion at higher velocities, they exhibit wave-like behavior. The associated wavelength of these matter waves is known as the De Broglie wavelength and is defined by the equation:

λ = h / p

Where:

• h is Planck’s constant (6.62 × 10^-34 m² kg/s),
• p is the momentum of the particle,
• m is the mass of the particle, and
• v is the velocity of the particle.

The De Broglie equation highlights the interaction between momentum and wavelength. The wavelength is inversely proportional to the particle’s momentum, implying that as the particle’s speed increases, the matter wave’s wavelength decreases. On the other hand, a lighter particle results in an increase in the De Broglie wavelength.

Wave Speed Formula

Wave Speed, denoting the overall distance travelled by a wave within a specific timeframe, is calculated using the formula:

v = λ/T = λ × f

Where,

• v is velocity of wave
• λ is wavelength
• T is Time Period
• f is Frequency of Wave

Different Types of Waves

Waves are classified into various types based on their diverse features.

• Based on Medium of Wave
• Based on Limitation of Motion
• Based on Dimension of Propagation

Classification Based on the Medium of Wave

Based on the medium of Wave Propagation, all waves can be classified as:

• Mechanical Waves
• Non-Mechanical Waves

Mechanical Waves

Mechanical Waves necessitate a medium for their propagation, implies that they must travel through a material substance. This reliance on a medium is evident in waves such as water waves, sound waves, and seismic waves. Their existence is linked to the collision and energy exchange among molecules within the medium.

Non-Mechanical Waves

Non-Mechanical Waves don’t need any medium for their transmission; it can propagate through a vacuum. These waves, including electromagnetic waves and matter waves, possess a transverse nature.

Classification Based on the Limitations of Motions

Based on the limitation of motion, waves are classified as

• Standing Waves
• Progressive Waves

Standing Waves

Standing Waves also called stationary waves show a unique characteristic of remaining stationary, no transfer of energy or momentum. Standing Waves involves the superposition of two harmonic waves, both possessing equal amplitude and frequency. These waves travel in opposite directions across the medium, resulting in the creation of stationary patterns. Standing waves are synonymous with stationary waves and are recognized by the presence of nodes and antinodes. At antinodes, the particle’s amplitude of vibration reaches its peak, while at nodes; it attains its lowest point.

Progressive Waves

Progressive waves are dynamic entities that facilitate the transfer of energy and momentum through wave motion. It also referred to as travelling waves; progressive waves show the ability to perpetually move forward without cessation or alterations in amplitude or direction. These waves are characterized by their dynamic and continuous nature, allowing them to convey energy and momentum through the medium in a seamless manner.

Classification Based on the Dimensions of Propagation

Waves show the diverse characteristics based on the number of dimensions through which they propagate energy. This classification distinguishes waves into three categories: One-Dimensional, Two-Dimensional, and Three-Dimensional.

One-Dimensional (1D) Waves

One-Dimensional Waves are those generated in a singular direction. Example of such waves is found in the oscillations of a spring.

Two-Dimensional (2D) Waves

Two-Dimensional Waves manifest in two dimensions. An example is observed in the undulations of water waves, where the energy travels across a surface.

Three-Dimensional (3D) Waves

Three-Dimensional Waves propagate energy across three dimensions. Prominent examples include electromagnetic waves and sound waves, where energy travels through space encompassing length, width, and height.

Some Other Types of Waves

Other than all these discussed types, there are some more waves, such as:

• Sound Waves
• Seismic Waves
• Water Waves

Sound Waves

Sound is characterized as a mechanical wave, propagates through a medium via vibrational motion. The essence of a sound wave lies in its creation as a disturbance that emanates from a source and travels outward. These waves, known as longitudinal waves, signify that the particle vibration aligns parallels with the energy wave propagation.

In the course of particle vibration, atoms oscillate a continual back-and-forth motion. This rhythmic movement establishes alternating high-pressure and low-pressure zones within the medium. These zones are termed compressions and rarefactions, respectively.

Seismic Waves

Seismic Waves are dynamic energy waves that traverse through the Earth, often triggered by natural events such as earthquakes, volcanic eruptions, significant landslides, or large man-made explosions. Scientists, known as seismologists, study these waves by capturing their recordings through instruments like seismometers, hydrophones (in water), or accelerometers.

The speed of Seismic Wave propagation is influenced by the density and elasticity of the medium. The velocity of these waves increases with depth through the Earth’s crust and mantle but experiences a dramatic reduction from the mantle to the outer core. Earthquakes produce various wave types, each with distinct velocities.

Seismic Waves can be broadly categorized into two types: Body Waves and Surface Waves.

Water Waves

Water Wave is characterized by particles moving in a circular pattern. Water Waves are prevalent on surfaces, exemplified by ocean waves and ripples in a cup of water. These surface waves combine longitudinal and transverse motions, with water molecules staying in fixed positions while distortions propagate at the wave speed.

Solved Example on Types of Waves

Example 1: If the Time Period of a Wave is 0.5 seconds, what is the Frequency of the Wave?

Solution:

Given the Time Period of the Wave as

T=0.5 seconds.

The relationship between Frequency (f) and Time Period is defined as

f= 1/T

Substituting the given Time Period into the formula:

f= 1/0.5 =2Hz

Therefore, the Frequency of the Wave is 2 Hertz.

Example 2: A wave has a wavelength of 700nm and frequency of 400THz. Find the velocity of the wave

Solution:

Given that,

wavelength = 700 nm = 700 × 10^-9 m

Frequency = 400 THz = 400 × 10¹² Hz

Hence, wave velocity = 700 × 10^-9 × 400 × 10¹² = 280000 × 10³ m/s = 2.8 × 10⁸ m/s

Practice Questions on Types of Waves

Q1. A Transverse Wave is transmitting energy from east to west. The movement of the particles in the medium will be:

a. Solely from east to west

b. Simultaneously in both eastward and westward directions

c. Strictly from north to south

d. In both northward and southward directions

Q2. A Wave is carrying energy from left to right, and the particles of the medium are oscillating back and forth in a leftward and rightward manner. This Type of Wave is identified as a:

a. Mechanical wave

b. Electromagnetic wave

c. Transverse wave

d. Longitudinal wave

Q3. A Sound Wave is classified as a mechanical wave rather than an Electromagnetic Wave. Why?

Q4. If a horizontal rod is struck vertically from above, what can be concluded about the Waves generated in the rod?

Q5. The Sonar device on a fishing boat uses underwater sound to detect fish. Would you anticipate sonar to be a Longitudinal or Transverse wave?

Types of Waves – FAQs

1. What is a Wave?

A Wave is the transmission of energy and momentum, with or without a material medium, from one location to another without physically moving the particles of the medium.

2. What are the Types of Waves?

The following are the Types of Waves:

• Mechanical Waves
• Electromagnetic Waves
• Matter Waves

3. Can Mechanical Waves propagate through Vacuum?

No, Mechanical Waves cannot propagate through vacuum. For example Sound Wave and Water Wave are mechanical wave and it requires a medium to propagate through.

4. What is the meaning of Non-Mechanical Waves?

Non-Mechanical Waves are that waves which do not require any medium to propagate through.

5. What are the Types of Mechanical Waves?

There are two Types of Mechanical Waves:

Longitudinal Waves: Longitudinal Waves are the waves in which the particles of the medium oscillate parallel to the direction of the wave’s motion.

Transverse Waves: Transverse Waves defined as undulations where the medium’s particles oscillate at right angles to the wave’s motion.

6. What type of wave is a sound wave Mechanical or Electromagnetic?

Sound wave is a form of Longitudinal Waves under Mechanical Wave.

7. What kind of Wave is Light?

Light Waves are Transverse waves in which the electric and magnetic fields do not deflect; It oscillates in the direction of the wave propagation.

8. What are the different Types of Earthquake or Seismic Waves?

There are two Types of Seismic Waves: Body Waves and Surface Waves. The Body Waves are further divided into Primary Waves (P-waves) and Secondary Waves (S-waves). Also, the surface waves are classified into Rayleigh Waves, love Waves and Stoneley Waves.

9. What are the different Types of Electromagnetic Waves?

The Electromagnetic Spectrum comprises a range of waves, each characterized by distinct wavelengths and frequencies. It’s important to note that wavelength and frequency are inversely related; as one increases, the other decreases. Within the electromagnetic spectrum, various types of waves are present. The primary categories of Electromagnetic Waves include Microwaves, Radio waves, Infrared rays, Ultraviolet rays, Visible light, Gamma rays, and X-rays.

10. What Factors determine the Velocity of a Mechanical Wave?

The Velocity of a Wave is governed by the characteristics of the medium through which it propagates.

11. Could you list the colors of visible light in order of increasing wavelength?

In ascending order of wavelength, the sequence of colors in visible light includes Violet, Indigo, Blue, Green, Yellow, Orange, and Red.