General Wave Behavior

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Introduction to Waves
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Table of Contents
Part A Definition
- Definition of waves.
- Basic Properties of waves.
Part B Types of Waves
and Terminology.
- Mechanical waves
Transverse and Longitudinal waves.
- Electromagnetic waves.
- Terminology of waves. Part
C The Wave Equation. Part D Common
Characteristic of Waves. Part E Revision
The basics
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PART ADefinition of wave

• A periodic 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.
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Basic properties of waves

• Energy is transferred from one place to another
  in a wave motion.
• Motion of the medium (particles of the medium) is
  usually periodically vibratory.
• Only the shape or form of wave travels, not the
  medium.

Remember to take notes
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PART B
TYPES OF WAVESWaves are classified into
different types according to their natures
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1. Mechanical Waves

• A material medium is necessary for the
  transmission for mechanical waves. Mechanical
  waves cannot travel through vacuum.
• Due to elastic forces on adjacent layers of
  medium, disturbance is transmitted from one layer
  to the next through the medium.

Click for examples
Water waves, sound, vibration of spring, etc.
click
And ...
according to the direction of vibration, waves
are also classified into (a) Transverse
wave (b) Longitudinal waves.
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1.1 Transverse Waves

• The waveform appears in the shape of sine curve.
• A wave in which the motions of the matter
  particles are perpendicular to the direction of
  propagation of the wave itself.

Examples
Water waves, pulse in a stretched
string,transverse wave demonstrator.
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1.2 Longitudinal Waves

• A wave in which the motions of the matter
  particles are in the same direction as the wave
  propagation.

Sound, or a spring oscillating up and down,
etc.Show magnetic longitudinal demonstrator
Examples
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2. Electromagnetic Waves

• Material medium is not essential for propagation.
  e/m waves travel through vacuum.
• Disturbance of electric and magnetic fields
  travelling through space.
• All electromagnetic waves are transverse waves.

examples
X-rays, radio waves, micro-waves,etc.
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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.
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• The amplitude is the maximum displacement of the
  medium from its equilibrium position.
• The wavelength (?) is the minimum distance
  between two points which are in phase.
• The frequency (ƒ) is the number of complete
  oscillations made in one second. Unit
  Hz
• The period (T) is the time taken for one complete
  oscillation. It is related to frequency by T
  1/ƒ Unit s

Table of Contents
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PART C
The Wave Equation
The wave velocity is the displacement traveled by
the wave in one second ....
Click to explore
The wave velocity (v) is related to frequency
and wavelength by --
v ƒ?
The Wave Equation
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Using the Wave EquationExample 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?
3.0 ƒ(0.6) i.e ƒ 5.0 Hz
Click to see the answer
Then the period of this wave is ???
Period T 1/ƒ T 1/5.0 or 0.2 s

Table of Contents
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PART D
Common Characteristics of Waves
Click to see
Click to see

• Transmission of energy
• Reflection
• Refraction
• Diffraction
• Interference

Wave
Wave
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Lets take water waves as an example to study the
characteristics of waves.
The behavior of water waves demonstrates all
these characteristics..
characteristics
Water Waves
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Reflection of Waves
Reflection of Waves
A travelling wave is reflected when it hits a
barrier.
This phenomenon can easily be observed when a
travelling waterwave hits a reflector in the
ripple tank.
Reflector
Reflected waves
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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 ?.
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Diffraction of Waves
When a travelling water wave hits an obstacle,
the wavefronts spreads out round the edge and
becomes curved. This phenomenon refers to
diffraction.
The wavelength of the wave is not changed in
diffraction.
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Interference of Waves
When two or more waves propagating in the same
medium meet at the same point, interference is
said to occur.
A stable interference pattern can be observed
when two water waves of same frequency meet one
another in a ripple tank.

Click for example

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All kinds of waves demonstrate these 5
characteristics.
We have seen that mechanical waves (water waves
in our example) well demonstrate these
characteristics.
Electromagnetic waves show all these
characteristics as well.
Think
It is known that light demonstrates all these
five characteristics of waves, do you think
that light exists in the form of wave ?
Click for answer
it is an electromagnetic wave.
Yes --
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PART E
Revision
Now you have learned the basic concepts of Waves.

• After this lecture, you should be ableto answer
  the following questions

Click here to go back to table of contents --gt
Are you ready ?
Next page
End the slide show
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1. What is the difference between mechanical and
electromagnetic waves ?
2. Can you give some examples of electromagnetic
waves ?
3. What is the direction of the particle motion
in a transverse wave ?
More questions
4. Is sound a transverse or longitudinal wave ?
5. Is it correct that water waves do not transmit
energy from one point to another ?
If you do not have all 5 questions answered
correctly, click here and back to part B again
if necessary ----gtgt
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1. In a wave diagram, can you identify the
following terms ? (a) wavelength (b)
amplitude.
2. Write down the wave equation.
3. What are the 5 common characteristics of waves
?
If you miss any of this questions, go back to
the lesson by clicking this button --gtgt
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Now we come to the conclusion of introducing
waves.
You should be able to tell the nature of waves,
and identify different types of waves after this
lecture.
mechanical
Waves
Electromagnetic
Waves
The study of waves is important in Physics.From
the motion of water to the structure of
atoms,study of waves applies almost in every
category.
THE END OF LECTURE