2. What is a wave?
 A disturbance that moves through matter or space.
 Energy moving from place to place.
 The matter or space that the wave travels through is
called a medium

3. Classification of waves
 There are two main categories of waves:
1. Mechanical Waves (our focus now )
~ Require a medium in order to transport their energy
from one location to another.
~ Ex: Sound
2. Electromagnetic Waves (we will look at these in more
detail next week)
~ EM waves are capable of transmitting energy through a
vacuum (i.e., empty space).
~ Ex – Photons of light

4. Mechanical Waves
 Two types of waves:
1. Longitudinal (aka Compressional)
•Longitudinal waves look like a slinky
•Direction of medium is parallel to the direction of wave
propagation (motion)
•Ex: Sound Waves - move air back and forth

5. Characteristics of a Longitudinal Wave
2 areas
Compression- an
area of high
molecular density and
pressure
Rarefaction - an area
of low molecular
density and pressure

6. Mechanical Waves
 Two types of waves:
2. Transverse
•Transverse waves look like a sine curve
•Direction of medium is perpendicular to direction of wave
propagation (motion)
•Ex: Water Waves - move stick up and down in a pond

7. Characteristics of a Transverse Wave
1)Crest- highest position
Crest of the wave
2) Trough- lowest
position of the wave
3) Wavelength- the
distance between two
‘like’ points on a wave
(crest to crest; trough
to trough)
4) Amplitude- Height of
Trough
the wave (from origin
to crest or trough)
5) Frequency- The
number of crests that
pass by a point each
second.

8. Measuring a Wave
Frequency vs. Period
 Frequency is how many  Period is the number of
waves pass by you (or an seconds (usually it’s less than
arbitrary point) per 1 second) it takes for 1 WAVE
second, measured in to pass by you, measured in
Hertz. seconds or seconds per wave.
1 1
f T
T f

9. Measuring a Wave
 Wave motion compared to linear motion
 Wavelength is comparable to displacement
 Period is comparable to time
 To find linear speed you use the equation:
distance
speed
time
v f
 To find wave speed do the same thing, just with wave variables:
wavelength( )
wave speed (v)
period ( )
Since frequency is the inverse of period you will usually see the
equation : wave speed = wavelength x frequency
Units: Since a “cycle” is not a standard unit this gives you m/s.

10. Stan and Anna are conducting a slinky experiment. They are studying
the possible affect of several variables upon the speed of a wave in a
slinky. Their data table is shown below. Fill in the blanks in the table.
Medium Wavelength Frequency Speed
Zinc, (1.75)(2)= 3.5m/s
1.75 m 2.0 Hz ______
1-in. dia. coils
Zinc, (0.9)(3.9)= 3.51m/s
0.90 m 3.9 Hz ______
1-in. dia. coils
Copper, (1.19)(2.1)= 2.499m/s
1.19 m 2.1 Hz ______
1-in. dia. coils
Copper,
0.60 m 4.2 Hz (0.6)(4.2)= 2.52m/s
______
1-in. dia. coils
Zinc, (0.95)(2.2)= 2.09m/s
0.95 m 2.2 Hz ______
3-in. dia. coils
Zinc, (1.82)(1.2)= 2.18m/s
1.82 m 1.2 Hz ______
3-in. dia. coils