What is a wave?
a wave is a disturbance that travels
through a medium from one location to
another.
A transfer of energy, not matter
2 Types of waves:
2
2 Types of waves:
Longitudinal vs. Transverse Waves
Longitudinal Waves
Wave particles move parallel to wave
Ex. slinky moving back and forth
Transverse waves
Wave particles move perpendicular to wave
Ex. slinky shaken up and down
Wave Characteristics
equilibrium
crest
amplitude
trough
•Equilibrium-The midpoint of a wave. Where the
medium would be resting if there were no wave
•Crest-Highest point above equilibrium
•Trough-Lowest point below the equilibrium
•Amplitude-displacement between the equilibrium
and EITHER a crest or trough.
Test your understanding
8m
2m
1. There are ____
4 crests and ____
3 troughs in the wave
above.
2. The equilibrium position is at ____
5 m.
3. The amplitude of the wave above is ____
3 m.
Wavelength
wavelength
wavelength
Wavelength – length of one cycle of wave
NOT length of entire wave
Ex. crest to crest, trough to trough
Symbol: l (lambda) units: meters (m)
Frequency
2m
8 m/s
Frequency (f) – number of cycles per second
Symbol: f
units: hertz (Hz)
Ex: How often does one cycle pass by if v
(speed) is 8 m/s and l is 2 m?
Equation
 8m/s = f (2m)
V=fl
Wave Period
2m
8 m/s
Period (T) – number of seconds per cycle
Symbol: T
units: seconds (s)
How often does one cycle pass by if v (speed)
= 8 m/s, l = 2 m and f = 4 Hz
Equation
f = 1/ T
4 = 1/T
Equations
v = l / T
velocity = wavelength/ Period
Like velocity = distance/time
f= 1/T
Frequency = one/ Period
v = f l
velocity = frequency * wavelength
Wave Interaction
Interference = is a type of interaction
Waves can interfere with one another
Waves do NOT effect one another’s movement.
During Interference,
The amplitude of the wave changes only when the
waves meet
the waves return to normal after the collision.
The combination wave is called a resultant wave
Constructive Interference
They will ADD together to produce a
greater amplitude.
This is known as CONSTRUCTIVE
INTERFERENCE.
Destructive Interference
This time when they add together they will
produce a smaller amplitude.
This is know as DESTRUCTIVE
INTERFERENCE.
Check Your Understanding
 Which points will produce constructive interference
and which will produce destructive interference?
 Constructive
G, J, M, N
 Destructive
H, I, K, L, O
Standing Wave
Has at least one fixed end (type of
boundary)
Fixed end: end of the medium that will
not be able to move.
Fixed End Animation
Free End Animation
15
Change in Medium
Think of a thin rope attached to a thin rope.
The point where the two ropes are attached
is the boundary.
 Part of the wave energy is transmitted to the more dense
medium, and part is reflected.
 The transmitted pulse is upright, while the reflected
pulse is inverted.
 The speed and wavelength of the reflected wave remain
the same, but the amplitude decreases.
 The speed, wavelength, and amplitude of the transmitted
pulse are all smaller than in the incident pulse.