[Physics Class Notes] on Types of Waves Pdf for Exam

A wave in simple words can be described as a disturbance that travels through a medium, transporting energy from one location i.e. its source to another location without transporting matter. Some examples of waves are waves caused by wind and water waves that move in a circular manner etc.

The water waves will mainly have two parts that are called a crest and trough through which the wave travels from one location to the other. Each crest will be followed by the other. The point on a wave with a maximum value of upward displacement within a cycle is called a crest and trough is the minimum or lowest point in a cycle.

Types of Waves

Usually, waves are around us, they can be sound waves, radio waves, water waves, sine waves, cosine waves, string waves, slinky waves, etc. These are created through disturbance. There are three types of waves. They are as follows:

Mechanical Waves:

These waves act as the propagation of a disturbance through the material medium owing to the repeated periodic movement of the particles of the medium about their mean positions, the disturbance being handed over from one particle to that of the other.

Momentum and energy propagate by the movement of particles of the medium. But the medium remains at the previous position and the mass transfer is not possible to take place here. The propagation can happen because of the inertia and elastic properties of the medium and these waves cannot travel through the vaccum.

Examples: Vibration of a string, tsunami waves, sound waves, ultrasounds, internal water waves, oscillations in spring and waves in slink, etc.

Mechanical waves are classified into two types. They are given below:

Transverse waves are the disturbance through a medium where the particles of the medium oscillate about their mean positions at right angles to the direction of propagation of the wave. This motion takes place and continues in a cyclical pattern or in a periodical pattern. 

The medium has particles that vibrate in a direction perpendicular to the direction of the propagation of the wave is a transverse wave. The formation of trough and crest takes place and there is also a possibility for polarization of a transverse wave. Examples of transverse waves are ripples on the water surface, vibrations in strings, etc. 

Following is the diagrammatic representation of the transverse wave in which the particles of the medium oscillate in a direction perpendicular to the direction of propagation:

During oscillation, the particles move upwards or downwards from the plane passing through their mean positions. The position of maximum positive displacement i.e the uppermost point of the wave is the crest. The position of maximum displacement i.e. the lowest point is called the trough. So, the crest and trough occur alternatively in a transverse wave.

The two directions that are independent of each other can be used as the wave direction. Example: when we hold a ribbon in our hand and move it upwards and downwards, it can create a transverse wave and by moving the hand sideways also the same thing happens. 

A wave is called longitudinal when a wave in which the particles of the medium oscillate about their mean positions in the direction of propagation of the wave.

The vibration of the particles of the medium for a longitudinal wave is in the direction of wave propagation. A longitudinal wave continues in the form of rarefaction and compression which is the compression and stretches in the same direction as that of the waves. 

At the places of compression, the density and pressure for a longitudinal wave tend to be maximum, and in the places of rarefaction, the density and pressure tend to be minimum. Only longitudinal waves can propagate in gasses. The longitudinal waves are also called compression waves.

Through a medium, a longitudinal wave travels in the form of compressions (C) and rarefaction (R). An area of the medium where the particles are compressed or come closer or distance between the particles becomes less than the normal distance between them is called a compression. In the region of compression, there is a temporary decrease in volume and a consequent increase in the density of the medium. 

A region of the medium in which the particles are rarefied or the particles move farther apart than their normal position is called a rarefaction. In the region of rarefaction, there is a temporary increase in the volume and a consequent decrease in the density of the medium. A wavelength is a distance between the centers of two consecutive compressions and two consecutive rarefactions. The time taken by a wave in order to complete one vibrational cycle or oscillation is referred to as the period of the wave. Examples of longitudinal waves are the Sound wave, ultrasound, glass vibrations, waves in a slink, and spring oscillations.

The earth’s internal structure is changing constantly over the years and evolving with time and this changing process is called differentiation. The planets in the universe are called elastic objects that are supported through wave propagation. These waves are body waves that can be either compressional or longitudinal and are called primary waves. S waves are the shear waves and they resemble the jello bowl and vibrations in it. The second wave that is being felt during earthquakes is called S waves.

Difference between Transverse Waves and Longitudinal Waves

Electromagnetic Waves:

Electromagnetic waves are the ones that are generated by the coupling of an electric field and a magnetic field. To both the electric and magnetic fields, these waves are perpendicular in direction and also perpendicular to each other. 

When there are periodic disturbances in the magnetic and electric fields, electromagnetic waves can be seen and these waves will have the frequency that comes in the range of the electromagnetic spectrum.

Electromagnetic waves don’t need a medium for their propagation. Also, these waves are transverse in nature and can also be polarized.

Properties of Electromagnetic Waves:

Following are the various properties of the electromagnetic waves:

• In a vacuum, the velocity of electromagnetic waves will be 3 × 108 m/ s

• In order for propagation, no existence of medium is required

• Electromagnetic waves travel with light velocity in vacuum

• They can be polarized and are transverse in nature and also have momentum

• EMW can exhibit interference and diffraction

• There is no deflection on account of an electric or magnetic field

Examples and Speed of Electromagnetic Waves:

Examples of Electromagnetic waves are Radio waves, X-ray, microwave, gamma rays, thermal radiation, etc. the electromagnetic waves together form the electromagnetic spectrum. These waves can have a particular nature when these waves are characterized by wavelength and frequency. EM would depend upon the refractive index of the medium.

Electromagnetic Spectrum:

Electromagnetic radiations are a form of energy that is discharged and absorbed by charged particles. The wave-like behavior is exhibited by these radiations when it travels through space. The electromagnetic waves have magnetic as well as an electric field that is orthogonal to each other and also to the propagation of the waves. 

These radiations are composed of several types of waves in different frequencies and wavelength regions and these are described with the help of the electromagnetic spectrum. The electromagnetic waves categorize the waves with different wavelengths and frequencies according to their uses, wave characteristics, and applications. Examples of Electromagnetic spectrum waves are Radio waves, Infrared rays, visible light, X-rays, etc.

Matter Waves:

Matter waves are also called De Broglie waves. They depict the wave nature of all matter, everything which makes up our body, atoms, etc. it is proven that the matter waves are very small and these waves are produced in electrons and particles. 

Various equations called the De Broglie equations basically suggest the dual nature of matter. The frequency of these waves is directly dependent on their kinetic energy. 

Surface waves are both mechanical in nature and also have electromagnetic nature. Example: A sea diving creature can create surface waves and they are also called Rayleigh waves.

Elastic waves are produced by bodies that are elastic in nature. The elastic body is responsible for the vibratory motion of the particles and the vibratory motion basically causes the elastic wave. The particles always tend to come back to their original positions when setting in wave motion in case of an elastic wave and this also propagates in the viscoelastic medium. The study of these elastic waves is referred to as Elastodynamics.

Learning the Types of Waves

The Types of Waves are not that difficult to learn and understand. It is one of the most important topics of your physics syllabus, which holds significant weightage in the exam. So, you can ensure maximum marks in questions based on waves and electromagnetism if you have a good understanding of the Types of Waves. Moreover, learning this concept will enhance your knowledge of physics. You can use the following tips to understand the Types of Waves completely: 

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