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The longitudinal waves in an earthquake are called pressure or P-waves, and the transverse waves are called shear or S-waves. These components have important individual characteristics; for example, they propagate at different speeds.
Physics. Waves. A wave is a disturbance in a medium that carries energy without a net movement of particles. It may take the form of elastic deformation, a variation of pressure, electric or magnetic intensity, electric potential, or temperature. Table of Content. Introduction of Waves. Types of Waves. Transverse Waves. Longitudinal Wave.
- 140 min
- Frequency of a wave is the number of waves passing a point in a certain time. The unit of frequency is hertz (Hz) which is equal to one wave per se...
- Amplitude is the maximum displacement from the neutral position. This represents the energy of the wave. Greater amplitude carries greater energy.
- Electromagnetic waves are the disturbance that does not need any object medium for propagation and can easily travel through the vacuum. They are p...
- Radio signals, light rays, x-rays, and cosmic rays are some of the examples of electromagnetic waves.
- Overview
- Types and features of waves
- Wave behaviour
- Reflection
- Refraction
- Diffraction
- Interference
- Doppler effect
- Standing waves
wave, propagation of disturbances from place to place in a regular and organized way. Most familiar are surface waves that travel on water, but sound, light, and the motion of subatomic particles all exhibit wavelike properties. In the simplest waves, the disturbance oscillates periodically (see periodic motion) with a fixed frequency and wavelengt...
Waves come in two kinds, longitudinal and transverse. Transverse waves are like those on water, with the surface going up and down, and longitudinal waves are like of those of sound, consisting of alternating compressions and rarefactions in a medium. The high point of a transverse wave is a called the crest, and the low point is called the trough. For longitudinal waves, the compressions and rarefactions are analogous to the crests and troughs of transverse waves. The distance between successive crests or troughs is called the wavelength. The height of a wave is the amplitude. How many crests or troughs pass a specific point during a unit of time is called the frequency. The velocity of a wave can be expressed as the wavelength multiplied by the frequency.
Britannica Quiz
Physics and Natural Law
Waves can travel immense distances even though the oscillation at one point is very small. For example, a thunderclap can be heard kilometres away, yet the sound carried manifests itself at any point only as minute compressions and rarefactions of the air.
Waves display several basic phenomena. In reflection, a wave encounters an obstacle and is reflected back. In refraction, a wave bends when it enters a medium through which it has a different speed. In diffraction, waves bend when they pass around small obstacles and spread out when they pass through small openings. In interference, when two waves ...
When waves hit a boundary and are reflected, the angle of incidence equals the angle of reflection. The angle of incidence is the angle between the direction of motion of the wave and a line drawn perpendicular to the reflecting boundary.
The speed of a wave depends on the properties of the medium through which it travels. For example, sound travels much faster through water than through air. When a wave enters at an angle a medium through which its speed would be slower, the wave is bent toward the perpendicular. When a wave enters at an angle a medium in which its speed would be increased, the opposite effect happens. With light, this change can be expressed by using Snell’s law of refraction.
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When a wave encounters a small obstacle or a small opening (that is, small compared with the wavelength of the wave), the wave can bend around the obstacle or pass through the opening and then spread out. This bending or spreading out is called diffraction.
The waves from two or more centres of disturbance may reinforce each other in some directions and cancel in others. This phenomenon is called the interference of waves. It is easy to see how this may happen. Consider two sources producing waves of the same wavelength and in phase; that is, at their origin the crests of the waves occur at the same t...
When the source of a wave moves relative to an observer, the observer notices a change in the frequency of the wave. This change is called the Doppler effect, after its discoverer, Austrian physicist Christian Doppler.
Consider a source emitting a wave such as light or sound of frequency ν moving away from an observer at velocity v. The successive crests of the light waves will reach the observer at longer intervals than if the observer were at rest, and calculation shows that the observer will receive them with a frequency ν(1−v/c), where c is the velocity of the wave. The frequency of the wave will appear to the observer slightly lower than it would if the source were at rest. If the source is approaching, the frequency will be higher.
If a wave is confined to a closed space, it undergoes both reflection and interference. For example, consider a tube of length l. A disturbance anywhere in the air in the tube will be reflected from both ends and produce in general a series of waves traveling in both directions along the tube. From the geometry of the situation and the finite constant value of acoustic velocity, these must be periodic waves with frequencies fixed by the boundary conditions at the end of the tube. The allowed frequencies of the waves in the tube satisfy sin kl = 0; i.e., the allowed frequencies are ν = nv/2l, where n is any integer and v is the acoustic velocity in the tube. These are the frequencies of harmonic waves that can exist in the tube and still satisfy the boundary conditions at the ends. They are called the characteristic frequencies or normal modes of vibration of the air column. The fundamental frequency (n = 1) is ν = v/2l.
The higher frequencies, called harmonics or overtones, are multiples of the fundamental. It is customary to refer to the fundamental as the first harmonic; n = 2 gives the second harmonic or first overtone, and so on. Approximately the same set of characteristic frequencies hold for a cylindrical tube open at both ends, though the boundary conditions are different.
- The Editors of Encyclopaedia Britannica
Different types of waves exhibits specific characteristics. These characteristics are used to distinguish between wave types. Orientation of particle motion relative to the direction of energy propagation is one way waves are characterized. There are three categories:
We can distinguish between two classes of waves, based on the motion of the medium through which it propagates. With transverse waves, the elements of the medium oscillate back and forth in a direction perpendicular to the motion of the wave.
In addition to amplitude, frequency, and period, their wavelength and wave velocity also characterize waves. The wavelength λ λ is the distance between adjacent identical parts of a wave, parallel to the direction of propagation. The wave velocity v w v w is the speed at which the disturbance moves.
One way to categorize waves is on the basis of the direction of movement of the individual particles of the medium relative to the direction that the waves travel. Categorizing waves on this basis leads to three notable categories: transverse waves, longitudinal waves, and surface waves.
