Year 11 Physics
8.2
Topic 3: The World Communicates
Start date: ________________
The World Communicates (Dot Point 1)
Contextual Outline
Humans are social animals and have successfully communicated through the spoken word, and then, as the use of written codes
developed, through increasingly sophisticated graphic symbols. The use of a hard copy medium to transfer information in coded
form meant that communication was able to cross greater distances with improved accuracy of information transfer. A messenger
was required to carry the information in hard copy form and this carrier could have been a vehicle or person. There was, however,
still a time limit and several days were needed to get hard copy information from one side of the world to the other.
The discovery of electricity and then the electromagnetic spectrum has led to the rapid increase in the number of communication
devices throughout the twentieth century. The carrier of the information is no longer a vehicle or person — rather, an increasing
range of energy waves is used to transfer the message. The delay in relaying signals around the world is determined only by the
speed of the wave, and the speed and efficiency of the coding and decoding devices at the departure and arrival points of the
message. The time between sending and receiving messages through telecommunications networks is measured in fractions of a
second allowing almost instantaneous delivery of messages, in spoken and coded forms, around the world.
This module increases students’ understanding of the nature, practice, application and uses of physics and current issues, research
and developments in physics.
Dot Point 1:
1.
1
The wave model can be used to explain how current technologies transfer information
1.1
describe the energy transformations required in one of the following:
– mobile telephone
– fax/modem
– radio and television
An energy transformation is a change in the type of energy, for example a change from sound energy to electromagnetic
waves.
Question 1a): Describe energy transformation in the mobile telephone: ______________________
_____________________________________________________________________________
Mobile telephone:
Question 1b) Define the terms energy and wave.
Question 2b) Explain how energy is transferred in a water wave without moving the individual water molecules.
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1.1.2 describe waves as a transfer of energy disturbance that may occur in one, two or three dimensions, depending on the
nature of the wave and the medium
Question 2: - Waves are carriers of energy. Waves may be 1D, 2D, or 3D. Examples of each include; laser light, which is a
one dimensional wave; water waves, which are two dimensional waves; and sound waves, which spread out in all directions
from a point, so are therefore three dimensional waves.
Complete the table to summarise one-dimensional (1-D), two-dimensional (2-D) and three-dimensional
(3-D) waves.
Types of waves
Example
Medium
Travels in one direction
along a
line
1-D
2-D
3-D
1.1.3
Description
Ripples on a pond
Air
identify that mechanical waves require a medium for propagation while electromagnetic waves do not
Mechanical waves, such as sound waves, water waves and earthquake waves need a medium (a substance) to travel through,
they cannot move from one point to another if there is nothing (a vacuum) between the two points. On the other hand
electromagnetic waves do not need a medium to travel through. An example of this is in space, which is a vacuum, if you call
out in space your sound waves do not penetrate out of your space suit. However electromagnetic waves do, therefore you can
see the light from the sun. Even simpler, in space you can see a planet explode, but you cannot hear it.
Question 3 (a) Identify the property that is common to all mechanical waves.
Question 3 b) Identify three examples of EM waves.
uestion 3 (c) Compare EM and mechanical waves. (Use a table – similarities, difference and examples)
1.1.4
define and apply the following terms to the wave model: medium, displacement, amplitude, period, compression,
rarefaction, crest, trough, transverse waves, longitudinal waves, frequency, wavelength, velocity
Medium: The substance through which the wave travels through.
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Displacement: Is the distance from the rest position to the wave particle at that instant.
Amplitude: The distance from the rest position to the highest crest or the lowest trough.
Period: The time it takes for one wavelength to pass a point. Period = 1/ frequency
Compression: In compression waves, the space where the particles are closest together.
Rarefaction: In compression waves, the space where the particles are furthest apart. Crest: The parts of the wave that are
above the rest position.
Trough: The parts of the wave which are below the rest position.
Transverse waves: Are forms of mechanical waves, they involve the particles vibrating perpendicular to the direction of the
wave.
Longitudinal waves: Are also forms of mechanical waves, and they involve the particles vibrating along the direction of the
wave.
Frequency: Frequency is the number of waves that pass a point in one second. Frequency = 1/period
Wavelength: The distance of one full wave. Velocity: The speed that the wave is propagating.
(see 1.1.6 for the relationship between velocity, frequency and wavelength)
Question 4 (a) Compare the direction of oscillation and the direction of energy transfer in a longitudinal wave and a transverse
Question 4 (b) Compare the direction of oscillation and the direction of energy transfer in a longitudinal wave and a transverse
wave. Use diagrams in your answer.
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Question 4 (c) Draw and label a diagram of a sinusoidal wave to clearly illustrate the crest, trough, amplitude and wavelength.
Use diagrams in your answer.
Question 4 (d) Draw and label a a sinusoidal wave to clearly illustrate the crest, trough, amplitude and wavelength.
http://www.bbc.co.uk/bitesize/standard/physics/telecommunications/communication_using_waves/revision/5/
http://www.softschools.com/quizzes/science/waves/quiz343.html
wave to clearly illustrate the crest, trough, amplitude and wavelength.
1.1.5describe the relationship between particle motion and the direction of energy propagation in transverse and longitudinal
waves
In longitudinal waves the particle motion is in the parallel to the direction of the energy propagation.
On the other hand in transverse waves the particle motion is perpendicular to the direction of the energy propagation.
1.1.6 quantify the relationship between velocity, frequency and wavelength for a wave: v  f The velocity of a wave is equal
to the frequency multiplied by the wavelength. v  f 𝑓 is in Hz, 𝜆 is in m and 𝑣 is in ms−1 .
V= velocity in m/s, f = frequency in Hertz and symbol is Hz
and 𝝺 = wavelength in metres
Question 5:
Imagine that you are on a boat in the middle of the ocean and you are bobbing up, down and
up again once every 2 s due to the water waves. You notice that the crests of the waves are
about 10 m apart.
(a) Calculate the frequency of the waves.
(b) Calculate the speed of the waves.

perform a first-hand investigation to observe and gather information about the transmission of waves in:
– slinky springs
– water surfaces
– ropes
or use appropriate computer simulations
(refer to practical booklet)
Question 6:
Increasing or reducing the tension in a rope can change the speed of a wave travelling along it. Predict how the
wavelength changes for a wave on the rope if:
a the frequency and speed are both halved
b the speed is doubled and the period remains the same
c the speed remains the same but the period is doubled.
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
present diagrammatic information about transverse and longitudinal waves, direction of particle movement and the
direction of propagation
1.2.2 perform a first-hand investigation to gather information about the frequency and amplitude of waves using an
oscilloscope or electronic data-logging equipment
(refer to practical booklet)
Name: ________________________________________
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Date: __________
Year `22 Physics Topic 2 Waves:
1.2.3 present and analyse information from displacement-time graphs for transverse wave motion
https://www.classzone.com/books/ml_science_share/vis_sim/wslm05_pg18_graph/wslm05_pg18_graph.html
http://www.animations.physics.unsw.edu.au//jw/oscillations.htm#physics
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Answer:
1.2.4 plan, choose equipment for and perform a first-hand investigation to gather information to identify the relationship
between the frequency and wavelength of a sound wave travelling at a constant velocity
1.2.4
solve problems and analyse information by applying the mathematical model of
v  f
to a range of situations
(see questions next page)
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Summary:
• Wave is any vibration (or oscillation) that can travel (propagate) from one place to another.
• Waves can be used to carry energy and information.
• A medium is an object or material through which the wave propagates, such as air for sound waves.
• All waves that require a material object as the medium are called mechanical waves.
• Transverse waves occur when the particles of the medium move (displace) at right angles to the direction of wave propagation,
such as waves on a rope.
• Longitudinal (or compression) waves occur when the particles of the medium move (displace) along the
same direction as the wave propagation; for example, compressing part of a slinky spring makes a longitudinal wave.
• The transfer of energy by a wave can take place in one, two or three dimensions, such as a rope (1-D), water
surface waves (2-D) or soundwaves (3-D).
• Electromagnetic waves can propagate in three dimensions and do not require a medium. In a vacuum,
these waves travel at the speed of light and are used in communication equipment, such as mobile phones.
• Electromagnetic waves include radio waves, microwaves, infra-red rays, visible light, ultraviolet rays, X-rays and
gamma rays.
• Electromagnetic waves are transverse waves, where the electric and magnetic fields are at right angles to each
other and to the direction of wave propagation.
• Mobile phone communication involves the transfer of energy between mechanical, electrical and electromagnetic energies.
• All waves can be described by combinations of sine waves.
• The maximum distance a particle oscillates from its equilibrium position (at either a peak or trough) is
the amplitude.
• The distance between a peak (or trough) and its nearest neighbour is called wavelength 𝜆.)
• The number of peaks (or troughs) that pass a point per second is called the frequency (f ). The unit of frequency
is cycles per second or hertz (Hz).
• The time in seconds between two adjacent peaks (or troughs) is called period (T ).
• Frequency is the reciprocal of period: f 
• Wave speed (v) is given by v f .
Quiz 1:
1. What is a wiggle in time called? ___________ What is a wiggle in space and time called? _________
2. What is the period of a pendulum? ___________________________________
3. What is the period of a pendulum that takes one second to make a complete back-and-forth vibration? ________
4. Suppose that a pendulum has a period of 1.5 seconds. How long does it take to make a complete back and forth
vibration? Is this 1.5-second period longer or shorter in length than a 1-second period pendulum? __________
5. How is a sine curve related to a wave? _____________________________
6. Distinguish among the different parts of a wave: amplitude, crest, trough, and wavelength.
Amplitude – ________________________ ;
crest – ______________________________ ;
trough ________________________;
wavelength – ________________________________
7. Distinguish between the period and the frequency of a vibration of a wave. How do they relate to one another?
Period – ________________________ ;
frequency – ___________________________
8. Does the medium in which a wave travels move along with the wave itself? ____________________
Defend your answer. ________________________________________________
9. How does the speed of a wave relate to its wavelength and frequency? _____________________________
10. As the frequency of sound is increased, does the wavelength increase or decrease? ________________ Give
an example. ___________________________________
11. Distinguish between a transverse wave and a longitudinal wave.
Transverse – ______________________________
longitudinal – ____________________________________________
12. The diagram shows a transverse wave.
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a) Which of A, B, C or D is:
i) the wavelength
ii) the amplitude
Classwork/ Homework:
1. Identify the main energy types used in the communication methods
listed below.
a satellite
b mobile phone
c television
d radio
e fax
2. Complete the following table to summarise the transmitter, transport medium/method and receiver for each device.
Device
TRANSMITTER
TRANSPORT
MEDIUM/METHOD
RECEIVER
Radio
Mobile phone
Landline phone
3. Classify each of the following as mechanical or electromagnetic (EM) waves and whether they are one-, two- or threedimensional.
Device
Radio
Mobile phone
Landline phone
4.
Dimension (1D, 2D or 3D)
Wave speed = frequency x wavelength
1.
2.
3.
4.
6.
7.
8.
9.
10.
Calculate the speed of a wave that has a frequency of 50 Hz and a wavelength of 4 m.
Calculate the speed of a wave that has a frequency of 200 Hz and a wavelength of 50 m
Calculate the speed of a wave that has a frequency of 6 Hz and a wavelength of 2000 m
Calculate the speed of a wave that has a frequency of 0.5 Hz and a wavelength of 0.2 m
Calculate the speed of a wave that has a frequency of 5 kHz and a wavelength of 4 m
Calculate the speed of a wave that has a frequency of 5 Hz and a wavelength of 50 cm
Calculate the speed of a wave that has a frequency of 2 M Hz and a wavelength of 4 m
Calculate the speed of a wave that has a frequency of 4 M Hz and a wavelength of 8 cm
Calculate the speed of a wave that has a frequency of 3 G Hz and a wavelength of 4 mm
Answer to Quiz 1:
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Mechanical or EM wave
1. What is a wiggle in time called? What is a wiggle in space and time called? A vibration; A wave
2. What is the period of a pendulum? Time for one complete cycle to occur
3. What is the period of a pendulum that takes one second to make a complete back-and-forth vibration? 1 s
4. Suppose that a pendulum has a period of 1.5 seconds. How long does it take to make a complete back and forth
vibration? Is this 1.5-second period longer or shorter in length than a 1-second period pendulum? 1.5 s; longer
5. How is a sine curve related to a wave? A sine curve is a pictorial representation of a wave
6. Distinguish among the different parts of a wave: amplitude, crest, trough, and wavelength. Amplitude –
maximum displacement; crest – point of greatest positive displacement; trough – point of greatest negative
displacement; wavelength – distance from one crest to the next
7. Distinguish between the period and the frequency of a vibration of a wave. How do they relate to one another?
Period – time to complete one cycle; frequency – how many cycles occur in a given time
8. Does the medium in which a wave travels move along with the wave itself? Defend your answer. No. The
disturbance, not the material itself, moves
9. How does the speed of a wave relate to its wavelength and frequency? Speed = wavelength x frequency
10. As the frequency of sound is increased, does the wavelength increase or decrease? Give an example.
Decreases; smaller musical instruments produce higher frequency sounds
11. Distinguish between a transverse wave and a longitudinal wave. Transverse – medium moves perpendicular to
wave direction; longitudinal – medium moves back and forth parallel to wave direction
Waves
Answer Question 1:
Relating this to the mobile telephone, it undergoes basic energy transformations of, sound wave (your voice), to electrical
energy (in the wires inside the phone), to electromagnetic waves (from the phone to the tower), to electrical energy (at the
tower), then to electromagnetic waves (to reach the receiving phone), then electrical energy (inside the receiving phone), then
to sound waves (at the speaker of the receiving phone).
Question 2:
Types of waves
Example
Medium
Travels in one direction
along a
line
1-D
2-D
3-D
Question 3:
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Description
Ripples on a pond
Air
Types of waves
Mechanical waves
2nd example
1st example
2nd example
1-D
2-D
3-D
Question 4:
Types of waves
similarities
differences
examples
Question 5:
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Quetsion 6
Example Problem: Question: An FM radio station transmits a carrier wave of frequency 103.2 MHz. Calculate the
wavelength of the signal.
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