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Context. The Unit draws together concepts from different areas of the Syllabus and applies them to some aspects of the gathering and communicating of
information. The Unit provides some insight into ways and means by which physics is applied in everyday life.
Outline. The first part of the Unit is concerned with the gathering and communicating of information. Sensing devices, processing units based on simple
electronic circuits and output devices are studied. The second part of the Unit is concerned with basic aspects of remote sensing in medicine. As such, Xrays, ultrasound and magnetic resonance are considered. Finally, the communicating of information is studied, leading to an appreciation of satellite
communication and the use of the mobile phone.
Online Resources. In this Unit, some suggestions are made for online resources. This list is by no means comprehensive but is intended as a starting point.
Students should be encouraged to research appropriate material for themselves and to share this information with their fellow students.
Learning Outcomes
Candidates should be able to:
Suggested Teaching Activities
Online Resources
Other resources
An Applications Support
Booklet is available from the
CIE Teacher Support website
and from CIE Publications.
This provides a guide to the
level of detail required.
Reference should be made
to the list of textbooks printed
in the Syllabus document.
Note that some texts are
more suitable as library
reference texts whilst others
are more suitable as
students texts and, in
particular, the ‘endorsed’
textbook.
All examples of examination
questions are taken from
9702 papers.
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Recommended Prior Knowledge. The study of ‘direct sensing’ requires a knowledge of basic current electricity and circuitry (AS, Unit 3). The section
entitled ‘remote sensing’ is involved with the production and use of X-rays and ultrasound and also the use of MRI. This will involve an understanding of
concepts of waves (AS, Unit 5) and magnetic fields (A2, Unit 3). Students should also be familiar with wave properties (AS, Unit 5) for the study of the
section based on ‘communicating information’.
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A2 Physics UNIT 6 Applications of Physics
28(b)
Learning Outcomes
Candidates should be able to:
show an understanding of the change in
resistance with light intensity of a lightdependent resistor (LDR).
Suggested Teaching Activities
Other resources
Experiment: Variation of resistance of an
LDR with distance of the LDR from a lamp.
28(c)
sketch the temperature characteristic of a
negative temperature coefficient
thermistor.
Experiment: variation of resistance of a
thermistor with temperature.
28(a)
show an understanding that an electronic
sensor consists of a sensing device and a
circuit that provides an output voltage.
Demonstration of potential divider circuit
incorporating either an LDR or a thermistor to
investigate how output p.d. across either the
fixed resistor or the LDR/thermistor depends
on environmental conditions.
28(d)
Online Resources
show an understanding of the action of a
piezo-electric transducer and its
application in a simple microphone.
Explanation/discussion:
 the structure of a quartz crystal
 distortion of the crystal and generation of a
voltage across the crystal
Note: this effect will be studied further when
studying the generation and detection of
ultrasound (29(h)).
28(e)
Describe the structure of a metal-wire
strain gauge.
Discussion as to basic structure.
Revision of R = L/A (AS Unit 3)
28(f)
relate extension of a strain gauge to
change in resistance of the gauge.
Effect of strain
Students should be aware of the simplifying
assumption that area of cross-section is
constant.
Discussion: uses of strain gauges.
28(g)
show an understanding that the output
from sensing devices can be registered as
a voltage.
This relates directly to the output from a
piezo-electric transducer or to the output from
a potential divider circuit (see 28(a)).
28(h)
recall the main properties of the ideal
operational amplifier (op-amp).
May be introduced by discussion of need to
process the voltage considered in 28(g).
Voltage may be small or there may be a need
to have an on/off situation.
Electronics as a series of integrated circuits.
The op-amp. No need to understand circuits
within the package but its
characteristics/properties must be known.
http://en.wikipedia.org/wiki/Pi
ezoelectric#sensors
http://www.recipeland.com/e
ncyclopaedia/index.php/Piez
oelectricity
Oct 2009, Paper 41, q.10
May 2008, Paper 4, q.9(a)
Oct 2007, Paper 4, q.8(c)
May 2010, Paper 42, q.10(a)
http://natmus.dk/cons/tp/strm
sr/strainm2.htm
May 2010, Paper 42, q.10(a)
Oct 2009, Paper 41, q.9(a)(b)
Learning Outcomes
Candidates should be able to:
Suggested Teaching Activities
28(i)
deduce, from the properties of an ideal
operational amplifier, the use of an
operational amplifier as a comparator.
Experiment: op-amp in open loop mode as a
comparator. Use with thermistor to monitor
temperatures. The output may be monitored
with a voltmeter or use of LEDs may be
introduced.
Slew rate may be introduced.
28(j)
show an understanding of the effects of
negative feedback on the gain of an
operational amplifier.
Discussion/ Experiment:
Saturation
Use of feedback to reduce gain
Negative feedback.
Effects of negative feedback, other than on
gain, should also be discussed.
28(k)
recall the circuit diagrams for both the
inverting and the non-inverting amplifier
for single signal input.
Experiments: Gain of inverting and noninverting amplifiers.
Input and output potentials.
An understanding of saturation.
28(l)
show an understanding of the virtual earth
approximation and derive an expression
for the gain of inverting amplifiers.
Discussion: the virtual earth.
Derivation of gain of inverting amplifier.
28(m)
recall and use expressions for the voltage
gain of inverting and the non-inverting
amplifiers.
Discussion; gain of non-inverting amplifier.
The derivation of this expression is not
required.
28(n)
show an understanding of the use of
relays in electronic circuits.
Discussion: typical output of processing unit
(28(a)). Relay can be used to
Switch large currents/voltages
Switch remotely
Examples of relays.
28(o)
show an understanding of the use of lightemitting diodes (LEDs) as devices to
indicate the state of the output of
electronic circuits.
Demonstration: the action of an LED.
The need of a protective resistor should be
discussed but will not be examined.
Use of two diodes on the output to indicate
high/low.
Online Resources
Other resources
Oct 2009, Paper 41, q.10
Oct 2007, Paper 4, q.8(a)(b)
May 2010, Paper 42, q.9(a)
May 2009, Paper 4, q.10(a)
Oct 2009, Paper 4, q.9(a)
May 2010, Paper 41, q.9(a)
May 2010, Paper 42,
q.9(b)(c)
May 2010, Paper 41, q.9(b)
May 2009, Paper 4,
q.10(b)(c)
Oct 2009, Paper 4, q.9(b)(c)
May 2010, Paper 42, q.10(b)
Oct 2009, Paper 41, q.10
May 2008, Paper 4, q.9(b)
Learning Outcomes
Candidates should be able to:
Suggested Teaching Activities
Online Resources
28(p)
show an understanding of the need for
calibration where digital or analogue
meters are used as output devices.
Experiment. Thermistor circuit with output as
a voltmeter. Calibration curve plotted.
(revision of AS, Unit 1).
Discussion of advantages/disadvantages of
non-linear scales e.g. fuel gauge.
http://www.nibib.nih.gov/eAd
vances/071305.htm
29(a)
explain in simple terms the need for
remote sensing (non-invasive techniques
of diagnosis) in medicine.
A brief discussion based on the history of
medical diagnosis may be helpful. What is
meant by non-invasive techniques and how
these have changed the face of medical
diagnosis.
http://www.plus2physics.com
explain the principles of the production of
X-rays by electron bombardment of a
metal target.
Students should be able to sketch a typical
X-ray spectrum and appreciate that there are
two components in the spectrum. They
should be able to explain the origins of these
components and recall and understand the
expressions
kinetic energy of electron = eV and eV = hc/λ
29(c)
describe the main features of a modern Xray tube, including control of the intensity
and hardness of the X-ray beam.
The roles of the tube current and the tube
voltage should be understood. The use of an
aluminium filter should be discussed. The
need to cool the target could lead to a
discussion as regards the efficiency of
production of x-ray photons.
29(d)
show an understanding of the use of Xrays in imaging internal body structures,
including a simple analysis of the causes
of sharpness and contrast in X-ray
imaging.
Students may be aware of the use of CCD’s
for the detection of X-rays, rather than
photographic film.
The difference between sharpness and
contrast should be emphasised.
The use of a variable sized aperture and a
lead grid should be discussed.
29(k)
recall and solve problems by using the
equation I = I 0 e-μx for the attenuation of
X-rays (and of ultrasound) in matter.
The meaning of attenuation should be
discussed. Factors affecting attenuation,
leading to the use of a contrast medium for
the use of X-rays with soft tissues (barium
sulphate for the stomach/intestines; radioopaque die for blood vessels).
29(b)
Other resources
www.med.harvard.edu/JPNM
/physics/refs/refs.html
www.colorado.edu/physics/2
000/xray
Oct 2009, paper 42, q.10(a)
http://dutch.phys.strath.ac.uk/
CommPhys2004Exam/Shelle
ywaugh/physics-xray.htm
Oct 2009, Paper 42, q.10(b)
http://www.compadre.org/info
rmal/items/detail.cfm?ID=547
Learning Outcomes
Candidates should be able to:
Suggested Teaching Activities
Online Resources
29(e)
show an understanding of the purpose of
computed tomography or CT scanning.
X-ray image as a ‘shadow’ or ‘flat’ image.
CT scan enables a 3D image to be formed
that can be rotated.
http://www.physicscentral.co
m/action/action-02-3.html
29(f)
show an understanding of the principles of
CT scanning.
Students should appreciate that a series of
X-ray images from different angles are
obtained for one thin ‘slice’. These are
processed by a computer to form an image of
the slice. Images of successive slices are
combined to form a 3D image.
http://www.colorado.edu/phy
sics/2000/tomography/
Other resources
May 2010, Paper 41, q.10(a)
www.moh.gov.ae/mohsite/xr
ay/
29(g)
show an understanding of how the image
of an 8-voxel cube can be developed
using CT scanning.
After an initial discussion, practice can best
be obtained by students working in small
groups.
http://www.sheffcol.ac.uk/link
s/Science/Physics/Medical/Ul
trasound/
May 2010, Paper 41, q.10(b)
29(h)
explain the principles of the generation
and detection of ultrasound waves using
piezo-electric transducers.
This can be an extension of the work already
covered in 28(d). The role of resonance
should be discussed.
www.ob-ultrasound.net/
May 2010, Paper 42, q.11
29(i)
explain the main principles behind the use
of ultrasound to obtain diagnostic
information about internal structures.
29(j)
show an understanding of the meaning of
specific acoustic impedance and its
importance to the intensity reflection
coefficient at a boundary.
When defining impedance, reference should
be made to the speed of the wave in the
medium.
Reflection at an air-tissue boundary and the
use of a gel should be discussed.
29(k)
recall and solve problems by using the
equation I = I 0 e-μx for the attenuation
(of X-rays and ) of ultrasound in matter.
Similarity of expression with attenuation of Xrays should be appreciated..
Received intensity at detector dependent on
reflection at boundaries and attenuation in
media.
May 2009, Paper 4, q.11(a)
Oct 2007, Paper 4, q.9(c)
May 2009, Paper 4, q.11(b)
Oct 2007, Paper 4, q.9(a)(b)
www.physics.union.edu/new
manj/2000/mri.htmdutch.phy
s.strath.ac.uk/.../MRI.htm
http://science.uniserve.edu.a
u/school/curric/stage6/phys/
medphys.html
May 2009, Paper 4, q.11(b)
Learning Outcomes
Candidates should be able to:
29(l)
explain the main principles behind the use
of magnetic resonance to obtain
diagnostic information about internal
structures.
Suggested Teaching Activities
It should be emphasised that magnetic
resonance is a nuclear process.
Online Resources
http://hsc.csu.edu.au/physics
/options/medical/3019/PHY9
64netdraft.html
Other resources
Oct 2009, Paper 41, q.11
May 2008, Paper 4, q.10
http://faculty.washington.edu/
chudler/nobel03.html
29(m)
http://physics.about.com/od/i
maging/
show an understanding of the function of
the non-uniform magnetic field,
superimposed on the large constant
magnetic field, in diagnosis using
magnetic resonance.
www.gcse.com/waves/radio.
htm
http://scienveworld.wolfram.c
om/physics/RadioWave.html
http://hyperphysics.phyastr.gsu.edu/hbase/class/p22
129.html
30(a)
understand the term modulation and be
able to distinguish between amplitude
modulation (AM) and frequency
modulation (FM).
It may be advantageous to commence this
Section with some revision of AS Unit 5.
30(b)
recall that a carrier wave, amplitude
modulated by a single audio frequency, is
equivalent to the carrier wave frequency
together with two sideband frequencies.
The frequency spectrum should be
introduced. Also, the spectrum produced
where the modulating signal is composed of
audio frequencies (speech).
Oct 2009, Paper 42, q.11(c)
Oct 2007, Paper 4, q.10(a)(c)
30(c)
understand the term bandwidth.
Examples for speech (telephone), music of
different qualities etc. should be discussed
Oct 2007, Paper 4, q.10(b)
30(d)
demonstrate an awareness of the relative
advantages of AM and FM transmissions.
30(e)
recall the advantages of the transmission
of data in digital form, compared to the
transmission of data in analogue form.
May 2010, Paper 41, q.11(a)
Oct 2009, Paper 42,
q.11(a)(b)
May 2008, Paper 4, q.11(a)
Oct 2007, Paper 4, q.10(a)
May 2010, Paper 41, q.11(b)
May 2008, Paper 4, q.11(b)
This could be introduced via digital
communication systems known to students
and why change-over from analogue to
digital.
Oct 2009, Paper 41,
q.12(a)(b)
Learning Outcomes
Candidates should be able to:
Suggested Teaching Activities
Online Resources
Other resources
30(f)
understand that the digital transmission of
speech or music involves analogue-to
digital conversion (ADC) on transmission
and digital-to-analogue conversion (DAC)
on reception.
It may be advantageous to introduce block
diagrams in preparation for 30(r). Any
transmission may also involve parallel-toserial and serial-to-parallel converters (again,
preparation for 30(r).
Oct 2009, Paper 41, q.12(c)
30(g)
show an understanding of the effect of the
sampling rate and the number of bits in
each sample on the reproduction of an
input signal.
Students should be familiar with the terms
step width and step height. They should be
able to sample an analogue signal, digitise it
and then plot the reconstituted analogue
signal.
Oct 2009, Paper 41, q.12(d)
30(h)
appreciate that information may be carried
by a number of different channels,
including wire pairs, coaxial cables, radio
and microwave links and optic fibres.
This can be achieved by asking students to
name different forms of communication and
then identifying the channel of
communication.
30(i)
discuss the relative advantages and
disadvantages of channels of
communication in terms of available
bandwidth, noise, cross-linking, security,
signal attenuation, repeaters and
regeneration, cost and convenience.
The relevant terms should be either revised
e.g. bandwidth or introduced e.g. noise.
Students should appreciate that some
properties of optic fibres are dependent on
the radiation employed.
http://collections.ic.gc.ca/sate
llites/english/index.html
30(j)
describe the use of satellites in
communication.
This should include the limits of world-wide
communication by alternative means e.g.
surface, sky and space waves.
http://www.smgaels.org/physi
cs/97/MGRAHLFS.HTM
30(k)
recall the relative merits of both
geostationary and polar orbiting satellites
for communicating information.
The work on satellites in A2 Unit 3 should be
revised to include the period and altitude of
satellites.
The uses of polar orbiting and of
geostationary satellites should be discussed
alongside their relative advantages and
disadvantages. Uses could include GPS,
television and telephone communication,
remote sensing.
30(l)
recall the frequencies and wavelengths
used in different channels of
communication.
May 2010, Paper 42, q.12(a)
May 2008, Paper 4, q.12(a)
http://physics.uwstout.edu/wx
/wxsat/types.htm
May 2010, Paper 41, q.12(b)
Learning Outcomes
Candidates should be able to:
Suggested Teaching Activities
Online Resources
The significance of a change of 3 dB may be
of use to students.
http://science.uniserve.edu.a
u/school/curric/stage6/phys/
world.html
Other resources
30(m)
understand and use signal attenuation
expressed in dB and dB per unit length.
30(n)
recall and use the expression
number of dB = 10 lg(P 1 /P 2 ) for the ratio
of two powers.
30(o)
understand that, in a mobile phone
system, the public switched telephone
network (PSTN) is linked to base stations
via a cellular exchange.
Oct 2009, Paper 42, q.12(a)
30(p)
understand the need for an area to be
divided into a number of cells, each cell
served by a base station.
Oct 2007, Paper 4, q.11(a)
30(q)
understand the role of the base station
and the cellular exchange during the
making of a call from a mobile phone
handset.
30(r)
recall a simplified block diagram of a
mobile phone handset and understand the
function of each block.
The making of a call includes the initial
switching on of the mobile phone as well as
the time during which the call is actively
taking place.
The role of the computer at the cellular
exchange is of importance.
May 2010, Paper 42, q.12(b)
May 2010, Paper 41, q.12(a)
May 2009, Paper 4, q.12
May 2008, Paper 4, q.12(b)
Oct 2009, Paper 42, q.12(b)
Oct 2007, Paper 4, q.11(b)
May 2009, Paper 4, q.13(b)
May 2009, Paper 4, q.13(a)