Wave (physics) facts for kids
A wave is a kind of oscillation (disturbance) that travels through space and matter. Wave motions transfer energy from one place to another.
Examples
Waves are found everywhere in the natural world. Examples of waves:
- water waves
- seismic wave (earthquakes)
- electromagnetic wave
Properties
Waves have properties that can be measured. All waves can be pictured by adding sine waves.
Sine waves can be measured too. The shape of a sine wave is given by its amplitude, phase, wavelength and frequency. The speed that the sine wave moves can be measured. The amplitude and wavelength of the sine wave are shown in the picture.
The highest point on a wave is called the crest. The lowest point is called the trough. The crest of a wave and the trough of a wave are always twice the wave's amplitude apart from each other. The part of the wave halfway in between the crest and the trough is called the baseline.
Complicated waveforms (like the sound waves of music) can be made by adding up sine waves of different frequencies. This is how mp3 audio files are converted from their compressed form into the music we can hear. Complex waves can be separated into sine waves by Fourier analysis.
Waves and matter
Some waves can move through matter while others cannot. For instance, some waves can move through empty space, light waves for example. Sound waves, on the other hand, cannot move through empty space. Inherently, all waves carry energy from one place to another when they move. In some applications of technology, waves may carry meaningful information from one place to another, such as news on the radio.
Usually, after a wave moves through matter, the matter is the same as it was before the wave was introduced, though in some cases, matter can be affected by waves traveling through it. In 1922, Louis de Broglie found out that all waves are also particles, and all particles are also waves.
Types
In matter:
- Transverse wave: the vibrations of particles are perpendicular ⊥ to the direction of travel of the wave. Transverse waves have crests and troughs. Wave crests and troughs move along a travelling transverse wave.
- Longitudinal wave: the vibrations of particles are parallel to the direction of travel of wave. Longitudinal waves have compressions and rarefactions. Compressions and rarefactions move along a travelling longitudinal wave.
- Standing wave: a wave that remains in a constant position.
- Travelling wave: The blue waves move off to the right. They are traveling waves. The red waves do not move. They are standing waves.
- Solitary wave or soliton: Solitary waves were first observed in a river channel in 1834. Something gets a bulge of water starting moving up the channel and the bulge on the surface of the water continues to move up the stream.
- Light waves can move through space. Light is different from wind or water because light sometimes acts like waves and sometimes it acts as little bits called "particles." The nature of light is a big part of quantum mechanics.
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Transverse wave
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Longitudinal wave
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Standing waves
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Travelling waves
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Solitary wave
Related pages
Images for kids
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Sound pressure standing wave in a half-open pipe playing the 7th harmonic of the fundamental (n = 4)
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Amplitude modulation can be achieved through f(x,t) = 1.00*sin(2*pi/0.10*(x-1.00*t)) and g(x,t) = 1.00*sin(2*pi/0.11*(x-1.00*t))only the resultant is visible to improve clarity of waveform.
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Sinusoidal waves correspond to simple harmonic motion.
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Standing wave. The red dots represent the wave nodes
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Light beam exhibiting reflection, refraction, transmission and dispersion when encountering a prism
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Sinusoidal traveling plane wave entering a region of lower wave velocity at an angle, illustrating the decrease in wavelength and change of direction (refraction) that results.
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Schematic of light being dispersed by a prism. Click to see animation.
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300 px
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A propagating wave packet; in general, the envelope of the wave packet moves at a different speed than the constituent waves.
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Animation showing the effect of a cross-polarized gravitational wave on a ring of test particles
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The red square moves with the phase velocity, while the green circles propagate with the group velocity
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A wave with the group and phase velocities going in different directions
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Identical waves from two sources undergoing interference. Observed at the bottom one sees 5 positions where the waves add in phase, but in between which they are out of phase and cancel.
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One-dimensional standing waves; the fundamental mode and the first 5 overtones.
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A two-dimensional standing wave on a disk; this is the fundamental mode.
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A standing wave on a disk with two nodal lines crossing at the center; this is an overtone.
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