CP PHYSICS
WAVES REVIEW
I.
Answer Key
Matching
A.
B.
C.
D.
E.
F.
crest
trough
medium
amplitude
wavelength
period
G.
H.
I.
J.
K.
frequency
mechanical wave
electromagnetic wave
longitudinal wave
transverse wave
L.
M.
N.
O.
P.
hertz
interference
reflection
refraction
diffraction
1.
B
the low point of a transverse wave
2.
H
waves that require a medium
3.
O
bending of a wave as it enters a new medium
4.
D
the maximum displacement of the wave from equilibrium
5.
I
waves that can travel through empty space
6.
L
unit for measuring frequency
7.
K
a traveling wave which causes matter to move perpendicular to the direction of the
wave
8.
E
the length of a wave from crest to crest or trough to trough
9.
P
bending of a wave around a barrier
10.
J
a wave which causes matter to move back and forth parallel to the direction of the
wave
11.
A
the high point of a transverse wave
12.
N
the bouncing back of a wave from a surface
13.
G
the number of waves that pass a certain point each second
14.
M
the result of waves moving through each other
15.
F
the time it takes for one complete vibration
16.
C
the material through which a wave travels
II.
Fill in the Blank
1.
A wave transfers ENERGY from one place to another.
2.
A wave with a great amount of energy has a large AMPLITUDE.
3.
Two waves travel through the same medium. They must have the same SPEED.
If the wavelength of wave “A” is four times that of wave “B”, the frequency of “A” is
¼ that of “B”.
CP PHYSICS, WAVES REVIEW, page 2
4.
Water waves are (transverse, longitudinal) and (electromagnetic, mechanical).
5.
Radio waves are (electromagnetic, mechanical) because they do not need a MEDIUM.
6.
All electromagnetic waves are (transverse, longitudinal).
7.
Refraction occurs because the new medium changes the wave’s SPEED.
8.
The angles at which a wave hits and reflects from a boundary are always EQUAL.
9.
Sound waves bend around a corner because their WAVELENGTH is large
compared to the size of the opening. This spreading is called DIFFRACTION.
10.
DAMPING is the decrease in the AMPLITUDE of a wave due to
energy lose in overcoming FRICTION and due to the spreading out of the
wave front.
11.
The period of a pendulum is affected by its LENGTH, not by its MASS
or AMPLITUDE.
12.
Waves reflected from a flexible boundary are (inverted, erect).
13.
Waves reflected from a rigid boundary are (inverted, erect).
14.
When a wave reaches a new medium which is very different from the old, most of the wave
will be REFLECTED and a little will be TRANSMITED.
15.
When a wave passes into a new medium, its FREQUENCY does not change, but
its WAVELENGTH and SPEED do change.
III.
Short Answer Questions
1.
A long spring passes along the floor of a room and out a door. A pulse is sent along the
spring. After a while, an inverted pulse of almost the same amplitude returns along the
spring. Is the spring attached to the wall in the next room or is it lying loose on the floor?
EXPLAIN.
It is attached to the wall because the wave comes back as an inverted pulse.
Inverted pulse occur when the wave hits a rigid boundary, like a wall.
2.
When a wave reaches the boundary of a new medium, part of the wave is reflected and
part is transmitted. What determines the amount of reflection?
The differences between the two media determines the amount of reflection.
The bigger the difference, the more reflection will occur.
3.
What occurs during constructive interference?
The crests of two waves meet and produce a larger wave by adding together.
CP PHYSICS, WAVE REVIEW, page 3
4.
What occurs during destructive interference?
The crest of one wave meets the crest of another wave. They either cancel each
other out or make a smaller wave.
5.
What is the major difference between mechanical waves and electromagnetic waves?
Mechanical waves need a medium while electromagnetic waves do not.
6.
What determines the speed of a mechanical wave?
The properties of the medium determine the speed of the wave.
7.
You stand in the back left corner of a racquetball court and hit the ball to the middle of the
front wall. Your opponent should stand where to return the ball? Why?
Your opponent should stand in the back right corner. The law of reflection states
that the angle of incidence equals the angle of reflection.
8.
What is the difference between a pulse and a wave train?
A pulse is a single wave disturbance while a wave train is made up of a series
of pulses which produce a continuous wave.
9.
What is the Doppler effect? What appears to happen to the wave’s frequency if the source
moves toward the receiver? away from the receiver?
The Doppler effect is the apparent change in frequency due to the motion of the
source and/or the receiver. The frequency increases as the source moves toward the
receiver, while the frequency decreases as the source moves away from the receiver.
10.
What are some practical uses of the Doppler effect?
speed radar, weather radar, hearing sirens, astronomy – determining how fast
objects are moving towards or away from Earth (Milky Way)
IV.
Problems
1.
The speed of sound in air is 346 m/s. A sound wave has a frequency of 750.0 Hz. What is
its wavelength?
v = 346 m/s
v = λf
f = 750 Hz
346 = λ(750)
λ=?
750
750
λ = 0.46 m
2.
It is observed that a wave crest hits the shore every 12 s. The distance between successive
crests is 3.2 m. What is the velocity of the wave?
T = 12 s
v = λ/T
λ = 3.2 m
v = 3.2/12
v=?
v = 0.27 m/s
3.
What is the frequency of a wave that has period of 3.75 seconds?
T = 3.75 s
f = 1/T
f=?
f = 1/3.75
f = 0.27 Hz
CP PHYSICS, WAVE REVIEW, page 4
4.
Waves of frequency 2.0 Hz are generated along a spring. The waves have a wavelength of
0.45 m.
a. What is the speed of the waves along the spring?
f = 2.0 Hz
v = λf
λ = 0.45 m
v = (0.45)(2)
v=?
v = 0.9 m/s
b. What is the wavelength of the waves along the spring if their frequency is increased to
6.0 Hz?
v = 0.9 m/s
v = λf
f = 6.0 Hz
0.9 = λ(6)
λ=?
6
6
λ = 0.15 m
5.
What is the period of a sound wave that has a frequency of 245 Hz?
f = 245 Hz
T = 1/f
T=?
T = 1/245
T = 0.0041 s
6.
What is the period of a pendulum on Earth if it has a string that is 0.85 m long?
L = 0.85 m
T = 2 √(L/g)
2
g = 9.8 m/s
T = 2 √(0.85/9.8)
T=?
T = 1.85 s
7.
What is the period of pendulum on the moon where gravity is 1.6 m/s2 if the length of the
pendulum is 0.75 m long?
L = 0.75 m
T = 2 √(L/g)
2
g = 1.6 m/s
T = 2 √(0.75/1.6)
T=?
T = 4.30 s
8.
The speed of a transverse wave along a slinky is 3.4 m/s. If the wave has a wavelength of
0.25 m, then what is its frequency?
v = 3.4 m/s
v = λf
λ = 0.35 m
3.4 = 0.35f
f=?
0.35 0.35
f = 13.6 Hz
9.
A sound wave travels 1200 m in 3.6 s. The period of its oscillation is 0.0045 s.
a. What is the speed of the sound wave?
d = 1200 m
v = d/t
t = 3.6 s
v = 1200/3.6
v=?
v = 333 m/s
b. What is its wavelength?
v = 333 m/s
v = λ/T
T = 0.0045 s
(0.0045)333 = λ (0.0045)
λ=?
0.0045
λ = 1.5 m
10.
What is the velocity of a water wave that has a wavelength of 14.8 m and a period of 1.2 s?
λ = 14.8 m
v = λ/T
T = 1.2 s
v = 14.8/1.2
v=?
v = 12.3 m/s