low frequency,
long wavelength
high frequency,
short wavelength
Frequency is the number of
waves that pass a given
point in a certain amount
of time.
How Frequency and Wavelength Are Related
The frequency and wavelength of a wave are related. When frequency
increases more wave crests pass a fixed point each second. That means
the wavelength shortens. So, as frequency increases, wavelength
decreases. The opposite is also true—as frequency decreases,
wavelength increases.
Suppose you are making waves in a rope. If you make one wave crest
every second, the frequency is one wave per second (1/s). Now suppose
you want to increase the frequency to more than one wave per second.
You flick the rope up and down faster. The wave crests are now closer
together. In other words, their wavelengths have decreased.
Graphing Wave Properties
The graph of a transverse wave looks much like a wave itself. The
illustration on page 451 shows the graph of an ocean wave. The measurements for the graph come from a float, or buoy (BOO-ee), that
keeps track of how high or low the water goes. The graph shows the
position of the buoy at three different points in time. These points are
numbered. Since the graph shows what happens over time, you can
see the frequency of the waves.
Unlike transverse waves, longitudinal waves look different from
their graphs. The graph of a longitudinal wave in a spring is drawn
below. The coils of the spring get closer and then farther apart as the
wave moves through them.
wavelength
Distance
between coils
wavelength
VISUALIZATION
CLASSZONE.COM
Watch the graph of a
wave form.
amplitude
The shape of the graph resembles the shape of a transverse wave.
The wavelength on a longitudinal wave is the distance from one
compression to the next. The amplitude of a longitudinal wave
measures how compressed the medium gets. Just as in a transverse
wave, frequency in a longitudinal wave is the number of waves passing
a fixed point in a certain amount of time.
How are longitudinal waves measured?
450 Unit 4: Waves, Sound, and Light