Waves are disturbances that transfer energy through a medium without transferring matter. There are two main types of waves: transverse waves, where the medium moves perpendicular to the wave motion, and longitudinal waves, where the medium moves parallel to the wave motion. Key properties of waves include wavelength, frequency, amplitude, and speed. The speed of a wave depends on the properties of the medium and can be calculated using the equation: speed = wavelength x frequency. Waves can change direction through reflection, refraction, and diffraction.

1. Waves and Wave Properties

2. Why are we able to see?
Answer: Because there is light.
And…what is light?
Answer: Light is a wave.
So…what is a wave?

3. A. Waves
Waves
–rhythmic disturbances that carry energy
through matter or space
Medium
–material through which a wave transfers
energy
–solid, liquid, gas, or combination
–electromagnetic waves don’t need a
medium (e.g. visible light)

4. A wave is a disturbance that carries
energy from place to place.
A wave does NOT carry matter with
it! It just moves the matter as it goes
through it.

5. B. Waves & Energy
Waves
– Carry energy
– Waves are caused
by vibrations
– Can do work
– Move objects
 Energy
 Waves carry energy
 Vibration is a transfer
of energy
 As waves carry energy
the particles in the
medium move
 the direction of the
motion determines the
type of wave

6. C. Categories of Waves
Mechanical
Waves
– Must travel through a
medium
– Cannot travel through
a vacuum
– Examples: sound,
ocean waves
Electromagnetic
Waves
 Does not require a
medium
 Can be transferred
through a vacuum
 Examples: light, UV
rays, Visible light

7. D. Types of Waves
Two Types:
Longitudinal Transverse

8. D. Transverse Waves
Transverse Waves
– medium vibrates
perpendicular to the
direction of wave
motion
– Examples: water
waves,
electromagnetic
waves

9. E. Longitudinal Waves
Longitudinal Waves (a.k.a. compressional
waves)
– medium moves in the same direction as the
wave’s motion
– Examples: sound waves, springs, slinky

10. B. Transverse Waves
Wave Anatomy
crests
troughs
wavelength
wavelength
amplitude
amplitude
corresponds to
the amount of
energy carried
by the wave
nodes

11. Some waves do not need matter (called
a “medium”) to be able to move (for
example, through space).
These are called electromagnetic waves
(or EM waves).
Some waves MUST have a medium in
order to move. These are called
mechanical waves.

12. Wave Types
1.Transverse waves: Waves in which the medium
moves at right angles to the direction of the wave

13. Parts of transverse waves:
Crest: the highest point of the wave
Trough: the lowest point of the wave

14. 2. Compressional (or longitudinal) waves:
Waves in which the medium moves back and
forth in the same direction as the wave

15. Parts of longitudinal waves:
Compression: where the particles are close together
Rarefaction: where the particles are spread apart

16. Wave Properties
Wave properties depend on what
(type of energy) is making the waves.
1.Wavelength: The distance between one point
on a wave and the exact same place on the
next wave expressed in meters

17. 2. Frequency: How many waves go past a point
in one second; unit of measurement is hertz (Hz).
The higher the frequency, the more energy in the
wave.
10 waves going past in 1 second = 10 Hz
1,000 waves go past in 1 second = 1,000 Hz
1 million waves going past = 1 million Hz

18. F. Measuring Waves
Frequency ( f )
– # of waves passing a
point in 1 second
– SI unit: Hertz (Hz)
shorter wavelength
 higher frequency
 higher energy
1 second

19. 1
Frequency = period ( )
or
period = the amount of time for one
cycle to do a complete motion
Frequency is measured in hertz (Hz).
1Hz = 1 wave per second
Cycle
second
F. Measuring Waves

20. F. Measuring Waves
Velocity ( v )
– speed of a wave as it moves forward
– depends on wave type and medium
v =  × f
v: velocity (m/s)
: wavelength (m)
f: frequency (Hz)

21. F. Measuring Waves
Solid
Molecules are close
together so waves travel
very quickly.
Liquid
Molecules are farther
apart but can slide past
one another so waves do
not travel as fast.
Gas
 Molecules are very far
apart so a molecule has
to travel far before it hits
another molecule, so
waves travel slowest in
gases.

22. 3. Amplitude: How far the medium moves from
rest position (where it is when not moving).
Remember that for transverse waves, the highest
point is the crest, and the lowest point is the trough.

23. Remember that for compressional waves, the
points where the medium is close together are
called compressions and the areas where the
medium is spread apart are called rarefactions.
The closer together and further apart the
particles are, the larger the amplitude.
compression
rarefaction

24. The energy of a wave is proportional to the
square of its amplitude. Mathematically
speaking . . .
E = CA2
Where:
E = energy (the capacity to do work)
C = a constant (depends on the medium)
A = amplitude
For example:
If the amplitude is equal to 3 units
(and we assume C = 1 for this case) . . .
E = (1) (3)2 = (1) (9) = 9 units

25. Note that when the amplitude of a wave is one
unit, the energy is one unit.
• When the amplitude is doubled, the energy is
quadrupled.
• When the energy is 10 times greater, the energy is
100 times greater!
Amplitude Energy
1 1
2 4
3 9
4 16
5 25
6 36
7 49
8 64
9 81
10 100
E = CA2

26. 4. Wave speed: Depends on the medium in
which the wave is traveling. It varies in
solids, liquids and gases.
A mathematical way to calculate speed:
wave speed = wavelength x frequency
(in meters) (in Hz)
OR
v = f x ‫ג‬
Problem: If a wave has a wavelength of 2 m and a frequency of 500 Hz,
what is its speed?

27. Answer: speed = 2 m x 500 Hz = 1000 m/s
Changing Wave Direction
1. Reflection: When waves bounce off a surface.
If the surface is flat, the angle at which the
wave hits the surface will be the same as the
angle at which it leaves the surface
(angle in = angle out).
This is the law of reflection.

28. 2. Refraction: Waves can bend.
This happens when a wave
enters a new medium and its
SPEED CHANGES.
The amount of bending
depends on the medium it is
entering.

29. 3. Diffraction: The bending of waves AROUND
an object.
The amount of bending depends on the size of
the obstacle and the size of the waves.
Large obstacle, small wavelength = low diffraction
Small obstacle, large wavelength = large diffraction

30. C. Diffraction
The bending of a
wave as it moves
around an obstacle
or passes through a
narrow opening.