is10_sb_unit_d

crest
rest position
wavelength
trough
wavelength
amplitude
Figure 10.6 All waves have a wavelength and amplitude.
Relationship between Frequency and Wavelength
Imagine you had a pan of water and you began gently tapping the
surface of the water (Figure 10.7). You would create a series of wave
crests. Suppose you made one new wave crest every second. Would it
take more energy or less energy to create three wave crests every
second? It would take more energy because you would need to tap
much faster.
When you create more wave crests per
second, the frequency of the wave increases.
As the frequency increases, the crests are closer
together. So, as more energy is put into making a
wave, the frequency of the wave increases and
the wavelength shortens. Frequency and
wavelength have an inverse relationship, which
means that when one value increases, the other
decreases. As frequency increases, wavelength
decreases. As frequency decreases, wavelength
increases.
There is a mathematical relationship among
the speed, v, the frequency f, and the wavelength
of the wave: v = f . For example, if the
wavelength of a wave is 10 cm and the frequency
is 5 cycles/s, then the speed is 50 cm/s.
Learning Checkpoint
1. Draw a wave and label:
(a) crest
(b) trough
(c) rest position
(d) wavelength
(e) amplitude
amplitude
dock
Figure 10.7 As the frequency of the wave increases,
wavelength decreases.
Light is part of the electromagnetic spectrum and travels in waves.
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