15.4 - Amplitude

Amplitude: The maximum displacement of a

particle in a wave from its equilibrium position.

Several terms discussed in earlier topics such as simple harmonic motion also apply to
waves, including amplitude.

At the right, you see a transverse wave caused by a hand shaking a string. The
amplitude of the wave is the distance between a particle at its maximum displacement í
a peak or trough í and the particle at its rest or equilibrium position. The horizontal line
in the diagram is the equilibrium position for the particles in the string. The amplitude by
convention is positive. Since amplitude is a distance, it is measured in meters.

A wave’s amplitude is related to the energy it carries. Waves with greater amplitude
carry more energy. You can experience this relationship at the beach; you may barely
notice a small-amplitude wave crashing into you, while a large-amplitude wave may
knock you off your feet!

Amplitude

Distance between rest point and

maximum displacement

·Height of peak

What is the amplitude of this

wave?

A = 0.20 m

15.5 - Wavelength

Wavelength: The distance between adjacent

peaks.

The wavelength of a wave is the distance between adjacent peaks in the wave. This will
be the same distance as that between adjacent troughs, or any two successive points
on the wave with the same vertical displacement and direction of particle motion.

The Greek letter lamda (Ȝ) represents wavelength. At the right, you see the wavelength
measured for a transverse periodic wave in a string. The unit for wavelength is the
meter.

Also on the right is a table that shows the wavelengths of a variety of waves. Wavelength

Distance between adjacent wave peaks

A variety of wavelengths

Copyright 2007 Kinetic Books Co. Chapter 15^297