Instructions
This presentation is designed to help you explore and understand some of the most common types of waves.
With regard to Earth science, wave motion describes the physical transmission of force or energy potential through a medium of transmission.
All waves can be described in terms of their amplitude, frequency and wavelength.
Background
AmplitudeThe term amplitude can have slightly different meanings depending upon the context of the situation. Its most general definition is that the amplitude is the maximum positive displacement from the undisturbed position of the medium to the top of a crest.
FrequencyFrequency refers to how many waves are made per time interval. This is usually described as how many waves are made per second, or as cycles per second. The SI unit for frequency is hertz (Hz).
WavelengthThe wavelength of a wave is the distance between any two adjacent corresponding locations on the wave train. This distance is usually measured from one crest to next.
Hydrosphere Lithosphere Atmosphere Biosphere
Waves in the Hydrosphere…
Any disturbance can cause a water wave. A pebble striking the surface, movement of a boat, movement of the earth during an earthquake, or the wind.
Ripples Swells Tsunamis
Ripples…
Also known as capillary wave, they occur when a wave travels along the interface between two fluids. Ripple dynamics are dominated by the effects of surface tension and have wavelengths typically less than a few centimeters.
Follow YouTube link (left) to see ripples produced from a pebble.
Swells…
Swells propagate away from their area of origin and naturally separate according to their direction and wavelength. They are large-scale and often irregular motions that form under sustained winds.
Tsunamis…
Tsunamis are a specific type of wave not caused by wind but by geological effects. In deep water, tsunamis are not visible because they are small in height and very long in wavelength. They may grow to devastating proportions at the coast due to reduced water depth.
Waves in the Lithosphere…
Commonly produced by earthquakes, waves in the lithosphere are usually referred to as seismic waves, which fall into two different categories:
Body Waves Surface Waves
Body Waves…
Body Waves travel through the interior of the Earth. They transmit the first-arriving tremors of an earthquake, as well as many later arrivals. There are two kinds of body waves:
Primary Secondary
2nd
Primary Waves…
P waves are longitudinal or compressionial waves, which means that the ground is alternately compressed and dilated in the direction of propagation. In solids, these waves generally travel almost twice as fast as S waves and are less destructive due to their bigger amplitudes.
Secondary Waves…
S waves are transverse or shear waves, which means that the ground is displaced perpendicularly to the direction of propagation. In the case of horizontally polarized S waves, the ground moves alternately to one side and then the other. S waves can travel only through solids, as fluids (liquids and gases) do not support shear stresses.
2nd
Follow YouTube link (left) to see a video with several examples of transverse waves.
Surface Waves…
Surface waves move more slowly than body waves and travel just under the Earth's surface. Because of their low frequency, long duration, and large amplitude, they can be the most destructive type of seismic wave. There are two types of surface waves:
Rayleigh Waves
Love Waves
Rayleigh Waves…
Named after Lord Rayleigh (pictured) in 1885, Rayleigh waves are generated by the interaction of P and S waves at the surface of the earth. Emanating outward from the epicenter of an earthquake, Rayleigh waves produced from earthquakes travel along the surface of the earth at about 10 times the speed of sound in air.
Love Waves…
Love waves are surface waves that cause horizontal shearing of the ground. Love waves take a long time to dissipate due to the huge amount of energy that they contain. For this reason, they are most destructive within the immediate area of the focus or epicentre of an earthquake. They are what most people feel directly during an earthquake.
Waves in the Atmosphere…
Radio Waves Rossby WavesSound Waves
Sound is transmitted through a medium (solid, liquid, gas, etc.) as longitudinal waves aka compression waves. Another way to think of sound is as vibration transmitted through air; particularly, sound means those vibrations composed of frequencies capable of being detected by ears. For humans, hearing is limited to frequencies between about 20 Hz and 20,000 Hz (20 kHz), with the upper limit generally decreasing with age.
Sound Waves…
Radio waves are electromagnetic waves occurring on the radio frequency portion of the electromagnetic spectrum. A common use is to transport information through the atmosphere or outer space without wires.
Radio Waves…
These waves are giant meanders in high-altitude winds (jet stream) whose emergence is due to shear in rotating fluids. When these loops become very pronounced, they detach the masses of cold, or warm, air that become cyclones and anticyclones and are responsible for day-to-day weather patterns at mid-latitudes. The waves were first identified in the Earth's atmosphere in 1939 by Carl-Gustaf Arvid Rossby who went on to explain their motion.
Rossby Waves…
Waves in the Biosphere…
Waves in the biosphere are those which are created by living organisms.
Hand Wave Audience Wave
The hand wave is a common way for human beings (as well as other members of the animal kingdom) to intentionally communicate awareness of each other's presence, to show attention to, and to suggest a type of relationship or social status between individuals or groups of people coming in contact with each other.
Hand Wave…
Audience Wave…
Achieved in a packed stadium when successive groups of spectators briefly stand and raise their arms. Each spectator is required to rise at the same time as those straight in front and behind, and slightly after the person immediately to either the right or the left. Immediately upon stretching to full height, the spectator returns to the usual seated position. The result is a "wave" of standing spectators that travels semi-rapidly through the crowd.
Follow YouTube link (left) to see a video of a wave at a soccer game in Stuttgart, Germany, or continue to find out more about audience waves.
Audience Wave…
In 2002, Tamás Vicsek of the Eötvös Loránd University, Hungary along with his colleagues analyzed videos of 14 waves at large Mexican football stadiums, developing a standard model of wave behavior. He found that it takes only the actions of a few dozen fans to trigger a wave. Once started, it usually rolls in a clockwise direction at a rate of about 12 m/s, or about 22 seats per second. At any given time the wave is about 15 seats wide. These observations appear to be applicable across different cultures and sports, though details vary in individual cases.
The original article can be found in Nature .
