Download World Communicates 07

8.2
The World Communicates
Assumed Knowledge
Domain: knowledge and understanding:
c
Refer to the Science Stages 4–5 Syllabus for the following:
5.6.1a
identify waves as carriers of energy
5.6.1b
qualitatively describe features of waves including frequency, wavelength and speed
5.6.1c
give examples of different types of radiation that make up the electromagnetic spectrum and identify some of
their uses
distinguish between the absorption, reflection, refraction and scattering of light and identify everyday
situations where each occurs
5.6.4a
5.9.1b
identify that some types of electromagnetic radiation are used to provide information about the universe
5.12c
describe some everyday uses and effects of electromagnetic radiation, including applications in
communication technology.
Physics PFAs (from table 7.1) in this module of work
P1. outlines the historical development of major principles,
concepts and ideas in physics
P2. applies the processes that are used to test and validate
models, theories and laws of science with particular
emphasis on first-hand investigations in physics
P3. assesses the impact of particular technological advances
on understanding in physics
P4. describes applications of physics which affect society or
the environment
Major concepts

Energy transformations

Energy transfer – including reflection, refraction
Models: transverse and longitudinal wave models,
mathematical models (equations e.g. v = f)
Theories: electromagnetic wave theory
Laws:
Inverse square law, Snell’s law, law of reflection

Production, modulation and reception of radio waves

Production of microwaves, digital encoding of information

Mobile phone, fax/modem, radio, television

Amplitude and frequency modulation, digital encoding

Optical fibre use – communication, medical (endoscopes)
P5. describes the scientific principles employed in particular
areas of research in physics
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The wave model can be used to
explain how current technologies
transfer information
 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
 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
1. Identify two types of waves that can be
produced in a spring and use
diagrams to clarify the difference
between these waves. (4M)
2. Compare surface water waves with a
transverse wave travelling through a
spring. (2M)
3. Discuss the usefulness of computer
simulations. (5M)
 describe the relationship between
particle motion and the direction of
energy propagation in transverse and
longitudinal waves
 present diagrammatic information about 4. Describe the relative motion of the
transverse and longitudinal waves,
particles and the direction of energy
direction of particle movement and the
propagation in a transverse wave.
direction of propagation
5. Describe the relative motion of the
particles and the direction of energy
propagation in a longitudinal wave.

 present and analyse information from
displacement-time graphs for
transverse wave motion
6. The adjacent diagram (a) shows a
displacement-time graph for a
transverse wave pulse travelling along
a spring. Interpret this graph. (2M)
7. A long spring was made to vibrate
 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

8. Contrast transverse and longitudinal
waves. (2M)
9. With the aid of a diagram, define the
terms amplitude, wavelength, crest
and trough of a transverse wave. (4M)
10. With the aid of a diagram, define the
terms amplitude, wavelength,
compression and rarefaction of a
longitudinal wave. (4M)
11. Define the terms frequency and period
of a wave and state how they are
related to each other. (3M)
12. Tabulate the following quantities,
showing the symbol for each quantity
the symbol for the quantity, the unit
used to measure that quantity and the
symbol for the unit: velocity,
frequency, wavelength, period,
amplitude. (5M)
 identify that mechanical waves require a
medium for propagation while
electromagnetic waves do not

13. Contrast the propagation of a
mechanical wave and an
electromagnetic wave.
14. List the components of the
electromagnetic spectrum in order of
increasing wavelength
 describe electromagnetic waves in
terms of their speed in space and their
lack of requirement of a medium for
propagation [from section 8.2.3]

15. Compare the speed of light and X-rays
in a vacuum. (1M)

 perform a first-hand investigation to
gather information about the frequency
and amplitude of waves using an
oscilloscope or electronic data-logging
equipment
16. Recount how you varied the frequency
of a wave and sketch the effect seen
on the CRO/data logging equipment of
changing only the frequency.
17. Sketch two waves having the same
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frequency but different amplitudes.
18. Describe the key features of a data
logger.

 plan, choose equipment for and perform 19. Propose a procedure that could be
a first-hand investigation to gather
followed to investigate the relationship
information to identify the relationship
between the frequency and
between the frequency and wavelength
wavelength of a sound wave. In your
of a sound wave travelling at a constant
answer, identify the independent and
velocity
dependent variables. (6M)
20. Describe how data obtained in a firsthand investigation was analysed to
identify the relationship between
frequency and wavelength of a sound
wave, and state the conclusion the
analysis produced. (4M)
 quantify the relationship between
velocity, frequency and wavelength for a
wave:
 solve problems and analyse information 21. The speed of sound in air is 340 m s-1.
by applying the mathematical model of
Calculate the wavelength of the
musical note, used as a reference tone
v  f
by musicians, having a frequency of
to a range of situations
440 Hz?
22. The velocity of electromagnetic
radiation is XXXXXX m s-1. Calculate
the wavelength of the radio waves
produced by NOVA 96.9, having a
frequency of 96.9 MHz.
23. Compare the wavelength of the radio
waves used by NOVA FM with the
wavelength of the microwaves
produced in a microwave oven, given
that these waves have a frequency of
XXXX gigahertz.
24. Astronomers gather information about
hydrogen in the universe using
electromagnetic radiation that gas
emits, which has a wavelength of
XXXX 8 cm. Calculate the frequency
of this radiation.
 describe the energy transformations
required in one of the following:
–
mobile telephone
–
fax/modem
–
radio and television

v  f
25. Identify the energy transformation that
takes place in the speaker of a mobile
phone. (1M)
26. Identify the energy transformation that
takes place in the antenna of a mobile
phone when it receives a signal. (1M)
27. Identify the energy transformation that
takes place in the battery of a mobile
phone. (1M)
28. Identify the component of a mobile
phone that converts sound energy into
electrical energy. (1M)
29. Identify the part of a mobile phone that
converts electrical energy to
electromagnetic energy in the form of
microwaves. (1M)
30. Outline the usefulness of converting
electrical energy to light energy in a
mobile phone. (2M)
2.
Features of a wave model can
be used to account for the properties
of sound
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31. Describe a sound wave. (2M)
32. Contrast a sound wave with an
electromagnetic wave. (4M)
 identify that sound waves are vibrations
or oscillations of particles in a medium

 explain qualitatively that pitch is related
to frequency and volume to amplitude of
sound waves
 perform a first-hand investigation and
33. Identify the physical property of a
gather information to analyse sound
sound wave that is responsible for the
waves from a variety of sources using
human perception of pitch. (1M)
the Cathode Ray Oscilloscope (CRO) or 34. What is the term used to classify
an alternate computer technology
sounds having a pitch higher than can
be heard by the human ear? (1M)
35. Identify the property of a sound wave
that is responsible for its volume
(loudness). (1M)
36. Propose two changes that could be
made independently of each other,
each of which could make an audible
sound inaudible. (2M)
37. The graphs in figure (a) represent
fig (a)
CRO traces of two sounds. Describe
the audible differences that a human
observer would hear between these
two sounds. (2M)
 explain an echo as a reflection of a
sound wave

38. Account for the production of an echo.
(2M)
39. Explain how an echo can be used to
determine the distance from an
observer to an object and state one
example of the use of this from the
natural world and an application of this
in medicine. (5M)
 relate compressions and rarefactions of
sound waves to the crests and troughs
of transverse waves used to represent
them

40. Using a quantitative time axis, graph
qualitatively the pressure changes at a
fixed point in a medium through which
a 100 Hz sound wave is travelling.
(2M)
41. A sound wave is sometimes
represented as a transverse wave.
Outline the significance of the “crests
and troughs” on such a graph. (2M)
42. The adjacent diagram represents a
sound wave traveling at 340 m s-1.
(a) Draw a corresponding transverse
wave to represent this wave at this
point in time. (2M).
(b) Draw a graph of the pressure
change at point “X”, showing the next
___ seconds.
 describe the principle of superposition
and compare the resulting waves to the
original waves in sound
 perform a first-hand investigation,
43. Describe in words the principle of
gather, process and present information
superposition as it applies to sound
using a CRO or computer to
waves.
demonstrate the principle of
44. Outline a first-hand investigation
superposition for two waves travelling in
carried out to demonstrate the
the same medium
superposition of waves. (3M)

 present graphical information, solve
problems and analyse information
involving superposition of sound waves
45. Draw a graph showing the waveform
that is produced by the superposition
of the two waves in the adjacent
graph. xxxx
3.
Recent technological
developments have allowed greater
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use of the electromagnetic spectrum
 identify the electromagnetic wavebands
filtered out by the atmosphere,
especially UV, X-rays and gamma rays

46. Identify three types of electromagnetic
waves that are strongly absorbed by
the Earth’s atmosphere.
47. Account for the need to conduct
investigations of objects in the
universe that produce X-rays using
detecting on board satellites in orbit
around the Earth.
 identify methods for the detection of
various wavebands in the
electromagnetic spectrum

48. Identify three methods of detecting
visible light. (3M)
49. Tabulate a method for detecting each
waveband in the electromagnetic
spectrum. (10M)
 explain that the relationship between
the intensity of electromagnetic
radiation and distance from a source is
an example of the inverse square law:
 plan, choose equipment or resources
for and perform a first-hand
investigation and gather information to
model the inverse square law for light
intensity and distance from the source
50. State the inverse square law for light
verbally. (2M)
51. Represent the inverse square law for
light using symbols.
52. The light intensity 2 m from a point
source is 18 milliwatts per square
centimetre. Calculate the light intensity
from the same source at a distance of
6 m.
53. Outline how the inverse square law
has been validated. (3M) [P2]
I
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
 analyse information to identify the
54. Identify the type of wave that carries
waves involved in the transfer of energy
information between a mobile phone
that occurs during the use of one of the
and the base station. (2M)
following:
55. Identify the type of wave most closely
–
mobile phone
associated with the operation of the
microphone and speaker in a mobile
–
television
phone. (1M)
–
radar
56. Identify the type of wave that allows
images to be viewed using a mobile
phone. (1M)
57. Compare the transmission of a
standard text message using a mobile
phone with the transfer of an mp3 file
from one phone to another using
Bluetooth. (4M)

 analyse information to identify the
58. Identify four communication
electromagnetic spectrum range utilised
technologies, each of which makes
in modern communication technologies
use of a different part of the
electromagnetic spectrum and identify
the type of wave used. (4M)
 outline how the modulation of amplitude
or frequency of visible light, microwaves
and/or radio waves can be used to
transmit information

59. Use a diagram to clarify how a sound
wave can be encoded using amplitude
modulation. (3M)
60. Outline the application of the principle
of superposition to the transmission
of information using AM radio. (3M)
61. Identify the type of modulation
represented by the diagram (left). (1M)
 discuss problems produced by the
limited range of the electromagnetic
spectrum available for communication
purposes

62.
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The World Communicates
Many communication
technologies use applications of
reflection and refraction of
electromagnetic waves


 describe and apply the law of reflection
and explain the effect of reflection from
a plane surface on waves
 perform first-hand investigations and
gather information to observe the path
of light rays and construct diagrams
indicating both the direction of travel of
the light rays and a wave front
63. State the law of reflection. (2M)
64. Draw a diagram to show the path of a
ray of light striking a plane mirror with
an angle of incidence of 20°.
 describe one application of reflection for
each of the following:
– plane surfaces
– concave surfaces
– convex surfaces
– radio waves being reflected by the
ionosphere
 present information using ray diagrams
to show the path of waves reflected
from:
–
plane surfaces
–
concave surfaces
–
convex surface
–
the ionosphere
65. Identify one application of reflection
waves from a plane surface. (1M)
66. Describe one application of reflection
of waves from a concave surface. (2M)
67. Identify the type of reflector that would
be useful at a “blind” intersection on a
road and outline the benefits that this
type of reflector produces. (3M)
68. FM radio stations in Sydney and
Melbourne may have the same
frequency, whereas AM station
frequencies are allocated in these
cities so that they are not the same.
Account for this with reference to the
ionosphere. (3M)
69. Compare the reflection of parallel rays
from a concave and a convex mirror
using ray diagrams. (4M)
70. Describe how applications of
reflection of light have affected
society. (4M) [P4]
 describe ways in which applications of
reflection of light, radio waves and
microwaves have assisted in
information transfer

71. Describe how applications of
physics have affected society. In
your answer, refer specifically to
light, microwaves and radio waves.
(6M) [P4]
 explain that refraction is related to the
velocities of a wave in different media
and outline how this may result in the
bending of a wave front
 perform an investigation and gather
information to graph the angle of
incidence and refraction for light
encountering a medium change
showing the relationship between these
angles
72. Account for the refraction of light
passing from one medium to another.
(2M).
73. Describe two situations in which light
passing from one medium to another
would not be refracted. (2M)
74. Identify the key difference that you
would observe between two graphs,
one plotting angle of incidence (i)
against angle of refraction (r) and the
other plotting sin(i) against sin(r) for
light passing from one medium to
another. (1M)

 perform a first-hand investigation and
gather information to calculate the
refractive index of glass or Perspex
75. Recount the procedure that you used
to gather first-hand information to
enable you to calculate the refractive
index of a transparent medium. In your
answer, identify the independent and
dependent variables as well as
variables that were kept constant. (6M)
76. Describe how you ensured that data
collected was valid. (2M)
77. How did you check the reliability of the
result you obtained for the refractive
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index? (2M)
 define refractive index in terms of
changes in the velocity of a wave in
passing from one medium to another

 define Snell’s Law:
 solve problems and analyse information 81. Calculate the angle of refraction when
using Snell’s Law
a ray of light travelling in air enters a
medium in which its velocity is
2 x 108 m s-1 at an angle of incidence
of 30°. (2M)
82. The path of a ray of light travelling in a
vacuum is changed by 5° when it
enters a medium at an angle of 40° to
the normal. Draw a diagram to
represent this and calculate the
velocity of light in the medium. (3M)
83. Light passed from a medium having a
refractive index of 1.7 into one having
a refractive index of 1.3. Calculate the
angle of incidence if the angle of
refraction was 89°.
84. When white light is passed through a
prism as shown in the adjacent
diagram, it is dispersed and a
spectrum is produced. State two
deductions, related to Snell’s law,
evident from this diagram.
85. The refractive index of liquid mercury
is 1.62. A ray of light travelling through
mercury (a very bright light!) strikes
the mercury-air interface at an angle of
30° as shown in the diagram.
Calculate the angle of refraction.
86. Outline how Snell’s law has been
validated. (3M). [P2]
v1 sin i

v2 sin r
78. Define refractive index of a medium in
terms of the velocity of light in a
vacuum and in the medium and write
this definition using appropriate
symbols. (2M)
79. Calculate the refractive index of glass
in which the speed of light is
2 x 108 m s-1. (2M)
80. The refractive index of water is 1.5.
Calculate the speed of light in water.
(2M)
 identify the conditions necessary for
total internal reflection with reference to
the critical angle
[Important for HSC course – Medical
Physics]

87. Use a labelled diagram to describe the
process of total internal reflection in an
optical fibre. (5M)
88. Identify the conditions necessary for
total internal reflection to occur. (3M)
 outline how total internal reflection is
used in optical fibres
[Important for HSC course – Medical
Physics]

89. Outline two applications of optical
fibres. (2M)
90. Describe how the application of
total internal reflection has affected
society. (5M) [P4]

91. Contrast the storage of information in
analogue and digital forms. (2M)
5. Electromagnetic waves have
potential for future communication
technologies and data storage
technologies
 identify types of communication data
that are stored or transmitted
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in digital form
92. Identify types of data that are stored or
transmitted in digital form. (3M)
93. Contrast the transmission of
information by an FM radio station with
the transmission of information by a
mobile phone. (6M)

 identify data sources, gather, process
94. Discuss some of the physical
and present information from secondary
principles applied in the operation
sources to identify areas of current
of the GPS. (6M) [P5]
research and use the available
95. Describe the effects on society of
evidence to discuss some of the
the application of physics to the
underlying physical principles used in
GPS. (5M) [P4]
one application of physics related to
waves, such as:
–
Global Positioning System
–
CD technology
–
the internet (digital process)
–
DVD technology


96. Identify three laws encountered in
this unit of work and describe how
laws are validated in physics. (5M)
[P2]
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