N o r t h E a st I n d ep en d e nt S c h o o l D i st ric t
8th Grade Science
Unit 5
Energy of Waves
Spring 2006
ENERGY of WAVES
This unit will be the first time waves have been introduced into the science
curriculum and talked about in depth. The 8th grade student needs to learn what a
wave is, how waves are generated, the different types of waves, characteristics of
waves and that they can travel through different media (medium).
A wave is a disturbance that transfers energy from one place to another. Energy
is defined as the ability to do work. Waves are produced when a force causes the
molecules in the matter to vibrate. A vibration is any action that repeats itself
over and over. Some waves require a medium to travel through. The material that
a wave travels through is called a medium. Gases, liquids, and solids are all
examples of media that are able to have waves travel through them. Students
should realize the many ways in which waves travel through media in the world
around us. There is a tendency for students to think of water when the word wave
is mentioned. Through this unit of study, students should also realize that waves
travel through the air in the form of sound and light and waves travel through
various layers of the earth as a result of seismic activity. Wave speed depends on
the medium through which the wave is traveling. Waves that require a medium in
which to travel are called mechanical waves. Two examples would be sound and
ocean waves. The particles of the medium do not travel with the wave. Some
waves do not need a medium to travel through. Electromagnetic waves such as
visible light, x-rays and microwaves would be examples of waves that do not need
to travel through a medium.
Three properties of waves are amplitude, frequency, and wavelength. The height
of the wave is its amplitude. The larger the amplitude the more energy the wave
has. For example, a sound wave with a higher amplitude will be louder. The number
of waves that pass by in a given amount of time is the frequency. In relation to
sound waves, a higher frequency creates a higher pitch. Wavelength is the
distance from one high point of the wave to the next high point of another wave.
Wavelength can also be measured from one low point in the wave to the next low
point in a wave. A wave that has a shorter wavelength will have more energy than a
wavelength with a longer wavelength.
Clarifying statements are intended to deepen teachers’ understanding of science concepts and serve as a guide for
instructional design. They are not intended to serve as student instructional materials.
This publication is the property of North East Independent School District. Duplication in whole or in part, outside of NEISD, is
prohibited without express written permission from NEISD.
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N o r t h E a st I n d ep en d e nt S c h o o l D i st ric t
8th Grade Science
Unit 5
Energy of Waves
Spring 2006
There are three methods by which waves travel. When classified according to
method of travel, waves are either transverse, longitudinal, or surface waves.

Transverse Waves: This type of wave causes the particles of the medium to
move in a direction that is perpendicular to the direction that the wave is
moving. This type of wave has high points known as crests and low parts
known as troughs. From one high point to the next high point is a measure
called the wavelength. The wavelength can also be measured from one low
point to the next low point. The higher a wave’s frequency, the shorter its
wavelength will be. Lower frequency waves produce longer wavelengths.
Electromagnetic waves are transverse waves which do not require a medium in
which to travel. Students should be familiar with forms of electromagnetic
waves and be able to interpret a diagram of the electromagnetic spectrum.
They do not need to memorize the spectrum.
Clarifying statements are intended to deepen teachers’ understanding of science concepts and serve as a guide for
instructional design. They are not intended to serve as student instructional materials.
This publication is the property of North East Independent School District. Duplication in whole or in part, outside of NEISD, is
prohibited without express written permission from NEISD.
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N o r t h E a st I n d ep en d e nt S c h o o l D i st ric t
8th Grade Science
Unit 5
Energy of Waves
Spring 2006
Source: http://www.lbl.gov/MicroWorlds/ALSTool/EMSpec/EMSpec2.html

Longitudinal Waves: This type of wave moves the particles in the medium in
the same direction that the wave is traveling. This causes the wave to have
areas of the medium where the particles are close together, known as
compressions, and areas where the particles are spread out, known as
rarefactions.
Sound is a type of energy that travels in longitudinal waves created by vibrating
objects. Sound cannot travel through a vacuum such as space since there are no
particles to squeeze together (compression) or spread apart (rarefaction). The
following illustrates how sound waves travel through air:
Clarifying statements are intended to deepen teachers’ understanding of science concepts and serve as a guide for
instructional design. They are not intended to serve as student instructional materials.
This publication is the property of North East Independent School District. Duplication in whole or in part, outside of NEISD, is
prohibited without express written permission from NEISD.
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N o r t h E a st I n d ep en d e nt S c h o o l D i st ric t
8th Grade Science

Unit 5
Energy of Waves
Spring 2006
Surface Waves: This type of wave is a combination of a longitudinal wave
and a transverse wave. This wave always forms between the boundaries of
two media. An example would be a surface ocean wave because it occurs
between the water and the air.
Clarifying statements are intended to deepen teachers’ understanding of science concepts and serve as a guide for
instructional design. They are not intended to serve as student instructional materials.
This publication is the property of North East Independent School District. Duplication in whole or in part, outside of NEISD, is
prohibited without express written permission from NEISD.
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