PAL (IGCSE) – PHYSICS
Section 3 Properties of Waves, including Light and Sound
Properties of Waves
Including Light and Sound
PAL (IGCSE) Single Science
Revision Book - Section 3
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PAL (IGCSE) – PHYSICS
Section 3 Properties of Waves, including Light and Sound
Syllabus Content_______________________________
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Section 3 Properties of Waves, including Light and Sound
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Section 3 Properties of Waves, including Light and Sound
Syllabus Details________________________________
3.1 General wave properties
Core
• Describe what is meant by wave motion as illustrated by vibration in ropes and springs and
by experiments using water waves
Oscillation
Water Surface
or Rope
Energy Transfer
Forced
oscillation
WAVE MOTION:
Waves carry energy without the net movement of particles
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Section 3 Properties of Waves, including Light and Sound
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Section 3 Properties of Waves, including Light and Sound
• Use the term wavefront
Waves in Water
Wave front diagram
Ray diagram
WAVEFRONT: Line connecting points with the same phase.
Displacement, x
• Give the meaning of speed, frequency, wavelength and amplitude
T
A
Time /s
Mean position
In Phase positions
Displacement, x
l
A
Position /m
One complete oscillation
Term
Amplitude
Frequency
Symbol
A
f
Wavelength
l
Wave speed
v
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Definition
Maximum displacement from the mean position
The number of oscillations that take place in 1
second
Shortest distance between two points in phase
with one another.
The speed at which wave fronts pass a
stationary observer
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Section 3 Properties of Waves, including Light and Sound
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Section 3 Properties of Waves, including Light and Sound
• Distinguish between transverse and longitudinal waves and give suitable examples
Transverse Waves
Oscillations perpendicular to
direction of energy transfer
Energy transfer
Longitudinal Waves
Oscillations parallel to
direction of energy transfer
Energy transfer
• Describe the use of water waves to show:
– reflection at a plane surface
Reflection at a plane surface
Normal
i
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r
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Section 3 Properties of Waves, including Light and Sound
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Section 3 Properties of Waves, including Light and Sound
– refraction due to a change of speed
Refraction in water
Wave Speed High
Deep water
Shallow water
Wave Speed Low
– diffraction produced by wide and narrow gaps
Diffraction
Supplement
• Recall and use the equation v = f λ
v=fl
v = velocity (wave speed)
f = frequency [Hz]
l= wavelength [m]
[m/s]
• Interpret reflection, refraction and diffraction using wave theory
See above
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Section 3 Properties of Waves, including Light and Sound
3.2 Light
3.2 (a) Reflection of light
Core
• Describe the formation, and give the characteristics, of an optical image by a plane mirror
Image:
• Imaginary
• Upright
• Same size as object
• Laterally inverted
• Same distance from the
mirror as the object
• Use the law angle of incidence = angle of reflection
Mirror Surface
Angle of Reflection
Angle of Incidence
Angle of Incidence = Angle of Reflection
Supplement
• Perform simple constructions, measurements and calculations
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Section 3 Properties of Waves, including Light and Sound
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Section 3 Properties of Waves, including Light and Sound
3.2 (b) Refraction of light
Core
• Describe an experimental demonstration of the refraction of light
A Stick in Water
Air
Water
• Stick appears closer to the surface of the water than it actually is
• Virtual Image
• Use the terminology for the angle of incidence I and angle of refraction r and describe the
passage of light through parallel-sided transparent material
normal
Refraction of Light
Glass block
Refraction of Light
normal
Incident ray
Angle of
Incidence
Less Dense Material
More Dense Material
Angle of
Refraction
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Refracted ray
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Section 3 Properties of Waves, including Light and Sound
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Section 3 Properties of Waves, including Light and Sound
• Give the meaning of critical angle
CRITICAL ANGLE: The angle of incidence beyond which light will totally internally reflect
• Describe internal and total internal reflection
Less dense
Partially transmitted
Grazing Emerging
Critical
angle
Totally Reflected
Partially reflected
More dense
• If the angle of incidence > critical angle light will totally internally reflect
Supplement
• Recall and use the definition of refractive index n in terms of speed
• Recall and use the equation sin i /sin r = n
normal
Incident ray
i
Air
Medium (n)
r
Refracted ray
Sin i
Sin r
= n
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v (air)
= n
v (medium)
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Section 3 Properties of Waves, including Light and Sound
• Describe the action of optical fibres particularly in medicine and communications technology
Optical Fibers
Optical Fibers
• Light is guided down the fiber.
• The light will always internally reflect if the angle of incidence > critical angle
• Optical fibers are used…
• for transmitting data
• for carrying pictures from inside the human body - ENDOSCOPE
3.2 (c) Thin converging lens
Core
• Describe the action of a thin converging lens on a beam of light
• Use the term principal focus and focal length
Converging Lens
Principle focus
f
Focal Length
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Section 3 Properties of Waves, including Light and Sound
• Draw ray diagrams to illustrate the formation of a real image by a single lens
Distant Object
CONVERGING LENS
Object
f
Image
f
Object at 2f
Object
f
f
f
f
Image
Object between 2f and f
Object
Image
Supplement
• Draw ray diagrams to illustrate the formation of a virtual image by a single lens
Object between f
Object
f
f
Object closer than f
Image
f
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Object
f
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Section 3 Properties of Waves, including Light and Sound
Distant Object
DIVERGING LENS
Object
f
Image
f
f
Image
f
Image
f
Object at f
Object
Object closer than f
Object
f
• Use and describe the use of a single lens as a magnifying glass
Magnifying glass
Image
f
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Object
f
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Section 3 Properties of Waves, including Light and Sound
3.2 (d) Dispersion of light
Core
• Give a qualitative account of the dispersion of light as shown by the action on light of a glass
prism
Dispersion of White Light by a Prism
red
blue


Increasing
Frequency
The refractive index is different for individual frequencies
The degree of refraction will increase with increasing frequency
3.2 (e) Electromagnetic spectrum
Core
• Describe the main features of the electromagnetic spectrum and state that all e.m. waves
travel with the same high speed in vacuo
Electromagnetic Spectrum
Wavelength
3 x 104 m
3 x 10-4 m
3m
3 x 10-12 m
3 x 10-8 m
Infrared
Gamma rays
Ultraviolet
Radio waves
X-rays
Microwaves
104 Hz
108 Hz
1012 Hz
1016 Hz
1020 Hz
Frequency
7.5 x 10-7 m
4 x 10-7 m
7.5 x 1014 Hz
4 x 1014 Hz
Visible Light
The speed of electromagnetic waves in a vacuum is constant
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Section 3 Properties of Waves, including Light and Sound
• Describe the role of electromagnetic waves in:
– radio and television communications (radio waves)
Radio Waves: Used to transmit radio and television signals from transmitters to houses etc.
The information is stored in the frequency and amplitude of the wave
Modulated Carrier Wave
For long distance transmission of signals…
• A high powered carrier wave is used
• A low intensity signal is added to the carrier wave
• The signal is carried ‘on the back’ of the carrier wave
Frequency Modulation
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Amplitidue Modulation
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Section 3 Properties of Waves, including Light and Sound
– satellite television and telephones (microwaves)
Microwaves:
Used to transmit data to and from land based and satellite receivers. These
transfer telephone and television signals. Microwaves are effective over long
distances
– electrical appliances, remote controllers for televisions and intruder alarms (infrared)
Infrared:


Used on remove controls for short transfer of data to the television from the
remote control
Detected by intruder alarms as IR is strongly emitted from hot objects like
humans
– medicine and security (X-rays)
X-rays:


Used to view inside humans as they are weekly absorbed by skin but more
strongly absorbed by bone
Used to view inside bags etc as weakly absorbed by the “skin” of a bag but
strongly absorbed by metallic objects like knives
• Demonstrate an awareness of safety issues regarding the use of microwaves and X-rays
Safety issues of microwaves:


Microwaves interact very strongly with water causing it to vibrate and so get
hot.
This will also happen inside the human body as we are predominantly water
Safety issues of X-rays:


X-rays are very high energy electromagnetic waves and will have an ionizing
effect on the human body.
Over exposure to X-rays can cause cancer
Supplement
• State the approximate value of the speed of electro-magnetic waves
Speed of electromagnetic waves in a vacuum: 300 000 000 m/s
• Use the term monochromatic
Monochromatic light: Light consisting of a single wavelength or frequency
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Section 3 Properties of Waves, including Light and Sound
3.3 Sound
Core
• Describe the production of sound by vibrating sources
• Describe the longitudinal nature of sound waves
Oscillation
Wave motion
Oscillating
Source



Air particles
The vibrating source “pushes” the air particles
The particles in front of the vibrating source also vibrate
A longitudinal wave is created
• State the approximate range of audible frequencies
Frequency Hz
0.1
1
Subsonic
10
100
1000
10000
Human Hearing
100000
1000000
ultrasonic
HUMAN HEARING RANGE: 20 – 20000 Hz
• Show an understanding that a medium is needed to transmit sound waves


Sound waves are vibrations in air particles
If there are no air particles present, no sound can be transmitted
• Describe an experiment to determine the speed of sound in air





Measure out a distance of a few 100 meters
Have one person with a starter pistol at one end of the measured distance
At the other end of the measured distance a person measures the time between
seeing the smoke from the starter pistol and hearing the sound
We can assume that the light from the smoke gets to the timer immediately as the
speed of light is much faster than sound.
The speed of sound can be calculated from the distance and time interval
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Section 3 Properties of Waves, including Light and Sound
• Relate the loudness and pitch of sound waves to amplitude and frequency
High frequency = High Pitch
Low frequency = Low Pitch
Low amplitude = Quiet
High amplitude = Load
• Describe how the reflection of sound may produce an echo
Echo
Sound waves
Supplement
• Describe compression and rarefaction
Longitudinal Waves
Compression
Rarefaction
COMPRESSION: Area of high pressure
RAREFRACTION: Area of low pressure
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Section 3 Properties of Waves, including Light and Sound
• State the order of magnitude of the speed of sound in air, liquids and solids
SPEED OF SOUND:



AIR
LIQUIDS
SOLIDS
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= ~340 m/s
= ~1500 m/s (water)
= ~5000 m/s (steel)
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