20.12.
Model:
The wave is a traveling wave.
Solve:
(a)
A comparison of the wave equation with Equation 20.14 yields:
A
=
3.5 cm,
k
=
2.7 rad/m,
ω
=
124 rad/s, and
. The frequency is
0
0 rad
φ
=
124 rad/s
19.7 Hz
2
2
f
ω
π
π
=
=
=
b)
The wavelength is:
2
2
2.33 m
2.7 rad/m
k
π
π
λ
=
=
=
(c)
The wave speed
45.9 m/s
v
f
λ
=
=
.
20.16 Visualize:
Please refer to Figure Ex
20.16.
Solve:
The amplitude of the wave is the maximum displacement which is 6.0 cm. The period of the wave is
0.60 s, so the frequency
1
1 0.60 s
1.67 Hz
f
T
=
=
=
. The wavelength is
2 m/s
1.2 m
1.667 Hz
v
f
λ
=
=
=
20.25.
Solve:
(a)
The frequency is
air
343 m/s
1715 Hz
0.20 m
v
f
λ
=
=
=
(b)
The frequency is
8
9
3.0
10
m/s
1.50
10
Hz
1.50 GHz
0.20 m
c
f
λ
×
=
=
=
×
=
(c)
The speed of a sound wave in water is
v
water
=
1480 m/s. The wavelength of the sound wave would be
7
water
9
1480 m/s
9.87
10
m
987 nm
1.50
10
Hz
v
f
λ
−
=
=
=
×
=
×
20.26.
Model:
Light is an electromagnetic wave that travels with a speed of 3
×
10
8
m/s.
Solve:
(a)
The frequency of the blue light is
8
14
blue
9
3.0
10
m/s
6.67
10
Hz
450
10
m
c
f
λ
−
×
=
=
=
×
×
(b)
The frequency of the red light is
8
14
red
9
3.0
10
m/s
4.62
10
Hz
650
10
m
f
−
×
=
=
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 Spring '10
 ZHOU
 Light, Frequency, Wavelength, Standing wave

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