Making Waves
Objectives
1. To investigate the basic nature of waves
and their properties.
2. Wave Properties: Speed, Wavelength,
Frequency, and Period.
3. Wave Phenomena: Reflection,
Interference, and Transmission.
4. Epic wave video
Ocean Waves
A wave is a traveling disturbance.
A wave carries energy from place to place
without any transfer of matter.
• Some waves such as mechanical waves
(eg sound waves) require a medium in
which to travel.
• Electromagnetic waves (eg. Light) are able
to travel through a vacuum ie they do not
require a medium.
• A pulse is a single wave of short duration.
• Most waves repeat the same motion in a
regular pattern – they are periodic.
Types of waves
Transverse waves
A transverse wave is one in which the disturbance is
perpendicular to the direction of travel (propagation) of the
wave.
Longitudinal Waves
Longitudinal wave is one in which the disturbance is parallel
to the line of travel (propagation) of the wave.
Example: Sound wave in air is a longitudinal wave.
State 2 differences between
sound and light waves
• 1. Sound is longitudinal, light is transverse
• 2. Sound requires a medium
Seismic Waves
Wave Type Motion of
particles
Velocity Other
characteristics
Longitudinal Same as
(P)
direction of
propagation
Faster
~6Km/s
Travel through
liquids
Perpendicular Slower
to direction of ~3Km/s
propagation
Do not travel
through liquids
Transverse
(S)
What is a periodic wave?
Periodic waves are waves that repeat.
Amplitude, Wavelength, and Period
The amplitude, A is the maximum disturbance.
The wavelength, λ is the horizontal length of one
cycle of the wave .eg. The distance between two
crests.
The period, T is the time required for one complete
up/down cycle of the wave.
The Wave velocity, v is the velocity of the wave
shape.
Frequency
The frequency, f is the number of waves passing any point each
second.
The frequency is measured in hertz (Hz)
Link
Wave Speed
Example
• Sound travels at 330 m/s in air. What will
be the wavelength of a note with
frequency 110 Hz?
Waves on a Rope
Pulses reflecting and transmitting
• Link
Superposition
• Link
• When 2 waves meet they can interfere
with one another.
• 2 peaks or troughs coinciding form a wave
twice as large – constructive interference.
• A peak and trough coinciding can “cancel”
each other – destructive interference.
• Another link
Standing waves
• If two waves of the
same amplitude,
frequency and speed
are produced from the
ends of a hollow pipe
or string then a
standing wave forms.
Nodes and antinodes
• Where two wave
peaks meet, a
maximum
displacement –
antinode – forms.
• Peak and trough
“cancel out” to form
node.
Diffraction
• Link
• As a wave passes an object diffraction
occurs – the wave bends.
• Longer the wavelength the greater the
diffraction.(Sound more than light)
• A gap between two obstacles the same
size as the wavelength gives maximum
effect.
Interference
Periodic Wave
Harmonic Wave
The Speed of Wave on a String
Guitar
The strings on a steel-string guitar have different weights, µ = m/L.
Q13
Principle of Superposition
When two or more waves are present simultaneously at the
same place, the resultant disturbance is the sum of the
disturbances from the individual waves.
Constructive Interference of
Sound Waves
Destructive
Interference
Standing Waves
Nodes and Antinodes
What determines the frequency of
a wave on a guitar string?
Making music with soft-drink bottles
Longitudinal Standing Waves
Musical instruments in the wind
family depend on longitudinal
standing waves in producing
sound. Since wind instruments
(trumpet, flute, clarinet, pipe
organ, etc.) are modified tubes
or columns of air, it is useful to
examine the standing waves
that can be set up in such tubes.
Standing-Wave Patterns
Doppler Effect
Doppler Effect