Waves
Many types of energy move from one place to another in waves. A wave is a disturbance that carries
energy from one place to another without carrying matter.
Wave Creation
Waves are created when a force, or an energy
source, creates a vibration or disturbance. For example, in the photo shown, the beaver's energy of
motion as it paddles its feet is transferred to the surrounding water, and waves are created. Waves
always start at the source and move away from it, so the waves are moving outward from the beaver.
Wave behavior can be described in terms of how fast the wave spreads and the distance between the
peaks of the disturbance. These two wave properties are called the frequency and the wavelength.
Waves Transmit Energy, Not Matter
A wave is moving energy. The energy in a wave is transferred from one point to another, but there is
no net movement of the matter through which the wave is traveling. Instead, the medium oscillates
back and forth. Sometimes this oscillation is in the direction of the wave's motion; other times, this
oscillation is perpendicular to the direction of the wave's motion.
Sound, light, and heat are some of the types of energy that move through waves. Earthquakes create
seismic waves that transmit energy through the interior of the Earth.
The following video demonstrates how particles of matter behave as waves move past them.
Clip provided by Education Clip Library with permission from ITN Source
Media & Wave Types
Waves can move through all types of matter, or media, and some waves can travel through areas—
such as the vacuum of space—that contain no matter at all. Waves can be classified as either
mechanical waves or electromagnetic waves based, in part, on whether or not a medium must be
present in order for them to travel.
Mechanical waves are waves that travel by making a substance, such as air or water, vibrate. If
there is no substance, as is the case in outer space, a mechanical wave will stop moving.
Sound waves, water waves, and seismic waves are all examples
of mechanical waves. Sound waves can travel in any type of matter, including air, water, walls, and
the human body. The energy in sound waves makes matter move by vibrating. Sometimes sound
vibrations are strong enough that you can feel an object vibrate. Water waves, such as those in the
ocean, carry energy in the motion of the water. When the water hits the land, the energy is transferred
to the land and causes weathering and erosion. Seismic waves are caused by earthquakes. When an
earthquake moves the land, it causes it to vibrate. The seismic vibrations carry energy through the
different layers of the Earth. These vibrations can be detected by scientists many hundreds of miles
away.
Electromagnetic waves, like the light produced by the Sun in the picture shown, are different from
mechanical waves in that electromagnetic waves can travel through the empty vacuum of outer
space.
However, like mechanical waves, they can travel through some
types of matter as well. Some electromagnetic radiation is what we call visible light. Other types of
electromagnetic radiation include radio waves, x-rays, gamma rays, microwaves, and infrared
radiation, and ultraviolet light.
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