PART A
Definition of wave:
• A ________ disturbance which travels
through a medium from one point in
space to the others.
Wave motion means the propagation of waves through a medium.
Wave motion appears in almost every branch of Physics.
Basic __________ of waves :
• ____________ is transferred from one place to another in a
wave motion.
• Motion of the medium (_______________) is usually
periodically vibratory.
• Only the -________________ of wave travels, not the medium.
PART B
_________________
Waves are classified into different types
according to _____________________ :
WAVES
Mechanical waves
Transverse waves
Electromagnetic waves
Longitudinal waves
Transverse waves
1. Mechanical Waves
• A _________ ______________ is necessary for the transmission
for mechanical waves. Mechanical waves cannot travel through
vacuum.
• Due to ________________ on adjacent layers of medium,
disturbance is transmitted from one layer to the next through the
medium.
Water waves, ________, vibration of spring, etc.
And ...
click
according to the direction of vibration, waves are also
classified into :
(a) Transverse wave;
(b) Longitudinal waves.
1.1 Transverse Waves
• The waveform appears in the shape of ___________________.
• A wave in which the motions of the matter particles are
_______________ to the direction of propagation of the wave
itself.
Water waves, pulse in a stretched
string,transverse wave demonstrator.
1.2 Longitudinal Waves
• A wave in which the motions of the matter particles are in the
_____________________ as the wave propagation.
___________, or a spring oscillating up and down,
etc.Show magnetic longitudinal demonstrator
_______________
Seismic waves use Earth itself as their medium. Earthquakes produce
them and so does a nation when it carries out an underground nuclear
test. (Other countries can detect them.) Seismic waves can be
longitudinal, transverse, or surface waves. P and S type waves are
called body waves, since they are not confined to the surface. Rayleigh
waves do most of the shaking during a quake.
Name
Type
Info
P Wave
_________
S wave
__________
Rayleigh
Wave
Love Wave
Surface
Also known as primary, compressional,
or acoustic waves; fastest seismic wave
Also known as secondary, or shear
waves; do not travel through fluids;
Rolls along surface like a water wave;
large amplitude
Ground moves side to side as wave
moves forward
Surface
Seismic Waves
Vibrations passing through the ground that result from an
earthquake
The seism focus generates spherical pulses
or primary (P) waves, which propagate like
concentric waves.
P waves have a longitudinal action; they cause change
in volume (compression and dilatation of the ground)
- Their velocity is high: 5 – 8 km/s.
S (secondary) waves, induced by P waves, are
transversal waves (soil oscillates perpendicular to direction)
- They are very destructive.
- Their velocity is around 3 – 5 km/s
2. Electromagnetic Waves
• _______________________ is not essential for
propagation. e/m waves travel through vacuum.
• Disturbance of electric and magnetic fields traveling
through space.
• All electromagnetic waves are __________ ___________.
__________, radio waves, microwaves,etc.
Electromagnetic Waves
Energy produced by the oscillation of an electric charge
which produces electric and magnetic fields
(spectrum is any range of wavelengths or frequencies)
X-Rays
- Discovered by accident in 1895 by German
scientist Wilhelm Conrad Roentgen while
experimenting with vacuum tubes
 A week later he took this x-ray of his wife
The Earth's atmosphere is thick enough that virtually
no X-rays are able to penetrate from outer space all
the way to the Earth's surface
Many things in space emit X-rays:
black holes, neutron stars, binary star
systems, supernova remnants, stars, the
Sun, and even some comets!
Supernova remnants in the
Small Magellanic Cloud
Terminology of a Wave
A wave is usually described by the following terms :
•
•
•
•
•
Amplitude
Wavelength ()
Frequency (f)
Period (T)
Wave velocity (v)
Each term will be explained….
• The ____________ is the maximum displacement of the
medium from its equilibrium position.
• The ____________ () is the minimum distance between
two points which are in phase.
• The ____________ (ƒ) is the number of complete
oscillations made in one second.
Unit : Hz
• The __________ (T) is the time taken for one complete
oscillation. It is related to frequency by T = 1/ƒ
Unit : ___________
The Wave Equation
The wave velocity is the displacement traveled by the wave in
one second ……....
The wave velocity (v) is related to
frequency and wavelength by --
The Wave Equation
Using the Wave Equation
Example :
A travelling wave of wavelength 0.6m moves at a speed of 3.0 m/s.
What is the period of this wave ?
Now you know  = 0.6 m, v = 3.0 m/s
Can you find the frequency of this wave……
By using the wave
equation,
v = ƒ
Then the period of this wave is ???
Period T = 1/ƒ
T = 1/5.0 or 0.2 s
Table of
Contents
•
•
•
•
•
Transmission of energy
Reflection
Refraction
Diffraction
Interference
Let’s take ______ ________ as an example
to study the characteristics of waves….
The behavior of water waves demonstrates
all these characteristics……..
characteristics
Reflection of Waves Reflection of Waves
A travelling wave is reflected when it hits a barrier.
This phenomenon can easily be observed when a traveling water
wave hits a reflector in the ripple tank.
Reflector
Reflected
waves
Reflection
The law of reflection: the angle of
incidence equals the angle of reflection
NOTE: Angles in optics
are taken from the normal
line to the surface
Refraction of Waves
- The speed of a water wave increases with depth. This change
in speed is accompanied by refraction.
This effect is a consequence of the wave equation, v = ƒ.
Since ƒ is constant, a decrease in v produces a decrease in .
Diffraction of Waves
When a traveling water wave hits an obstacle, the wave fronts
spreads out round the edge and becomes ____________.
This phenomenon refers to diffraction.
The __________ of the wave is not changed in diffraction.
Interference
• when two waves are combined, either
constructive or destructive interference can
occur.
__________
interference
____________
interference
_____________
• a transverse wave is
linearly polarized with
its vibrations always
along one direction
• a linearly polarized
wave can pass through a
slit that is parallel to the
vibration direction
• the wave ______ pass
through a slit that is
perpendicular to the
vibration direction
Polarizing sunglasses
is known as
___________
Properties of Sound
• A sound is a ____________
• The vibrating causes the air molecules near the
movement to be forced closer. This is called
_____________________
• As the vibration moves on, the density and air pressure
becomes lower than normal and is called ____________
• Pressure wave – _______________
• Frequency = pitch
• v = 334 m/s in air at room temperature
• Velocity is dependent upon the ______________
Can
affect
speed
Do molecules move faster or slower
as temperature increases?
So would sound travel faster or slower as
temperature increases?
•requires a medium
(cannot travel in a
vacuum)
Solid
Liquid
Waves travel fastest in _______,
slowest in _______________.
Gas
•Fastest in ______, slowest in ________.
Air = 340 m/s
water= 1440 m/s
steel = 5000 m/s
•Supersonic: faster than the
speed of sound.
• Sound travels faster in warm water than in cold water
• By measuring the time it takes for sound to travel a
known distance through the ocean the average
temperature of the water can be calculated = ATOC
(acoustic thermometry of ocean climate)
Speeds of Sound
at T = 20 C
•
•
•
•
•
•
•
•
Air
Helium
Hydrogen
Water
Sea water
Iron/Steel
Glass
Aluminum
•
•
•
•
•
•
•
•
343 m/s
1005 m/s
1300 m/s
1440 m/s
1560 m/s
≈5000 m/s
≈ 4500 m/s
≈ 5100 m/s
The highness or lowness of sound.
Depends on the _______________of sound
waves.
High frequency = High pitch
Low frequency = Low pitch
•Also called ________________
•Amount of energy
•Depends on the ______________ of sound
waves. (amplifier)
Large Amp. = Loud sound
Small Amp. = Soft sound
Intensity of Sound
• Unit is the _________. Named after
Alexander Graham Bell
• More commonly used is the decibel (dB)
= 0.1 Bel
Some Intensities (in dB)
•
•
•
•
•
•
•
•
Jet plane at 30 m
Threshold of pain
Indoor rock concert
Auto interior
Street traffic
Conversation
Whisper
Rustle of leaves
•
•
•
•
•
•
•
•
140
120
120
75
70
651
45
20
•Sound waves reflecting from hard surfaces
•Ex.: Multiple echo resulting from the direct
sound AND the reflected sound
Reverberation vs Echo
Animations courtesy of Paul Hewitt
and borrowed from physicsclassroom.com
Sound is a pressure wave
Animations courtesy of Paul Hewitt
and borrowed from physicsclassroom.com
Resonance
• Forced vibrations
• Something makes something else vibrate
that has the same natural frequency.
Ear
Tuning fork
creating a sound wave
Animations courtesy of Paul Hewitt
and borrowed from physicsclassroom.com
____________
• Ultrasound can be used to create internal
images of the human body
• Ex. Pregnant woman gets a “picture” of her
unborn baby
• Caused by destructive interference
• Result – hardly any or no sound
• Bad for concert halls – designers be
careful!
Used to locate underwater
objects and distances.
***Reflection**
________________
• Apparent change in frequency (pitch) of a
sound from a moving source.
• Source moving toward observer:
• Source moving away from observer:
__________________________
*Moving towards increases the
pitch
*Moving away decreases the pitch
*Think of sirens