EDEXCEL IGCSE / CERTIFICATE IN PHYSICS 3-1 Properties of Waves

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EDEXCEL IGCSE / CERTIFICATE IN PHYSICS
3-1Properties of Waves

• Edexcel IGCSE Physics pages 91 to 98

Content applying to Triple Science only is shown
in red type on the next slide and is indicated on
subsequent slides by TRIPLE ONLY
June 17th 2012
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Edexcel Specification

• Section 3 Waves
• b) Properties of Waves
• understand the difference between longitudinal
  and transverse waves and describe experiments to
  show longitudinal and transverse waves in, for
  example, ropes, springs and water
• define amplitude, frequency, wavelength and
  period of a wave
• understand that waves transfer energy and
  information without transferring matter
• know and use the relationship
• wave speed frequency wavelength v f ?
• use the relationship frequency 1 / time
  period f 1 / T
• use the above relationships in different contexts
  including sound waves and electromagnetic waves
• understand that waves can be diffracted when they
  pass an edge
• understand that waves can be diffracted through
  gaps,
• and that the extent of diffraction depends on the
  wavelength and the physical dimension of the gap.

Red type Triple Science Only
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Waves

• A wave is a means of transferring energy and
  information from one point to another without
  there being any transfer of matter between the
  two points.

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Transverse Waves

• Transverse waves are waves where the direction of
  vibrations is at 90 to the direction in which
  the wave travels.
• example water waves

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Longitudinal Waves

• Longitudinal waves are waves where the vibrations
  of the particles are along the direction in which
  the wave travels.
• example sound waves

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Describing Waves1. Amplitude (A)

• Amplitude is the maximum movement of the
  particles that make up a wave from their rest
  position.

The amplitude is the height of a crest OR the
depth of a trough
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2. Wavelength (?)

• Wavelength is the distance between one wave peak
  and the next wave peak along the path of a wave.
• Wavelength is measured in metres.

Wavelength is also the distance between the
bottom of one trough to the next.
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3. Frequency (f )

• Frequency is the number of wave peaks that pass a
  point in one second.
• Frequency is measured in hertz (Hz)
• 1 Hz 1 peak per second
• 2 Hz 2 peaks per second and so on.
• 1 kilohertz (1kHz) 1 000 Hz
• 1 megahertz (1MHz) 1 000 000 Hz
• 1 gigahertz (1GHz) 1 000 000 000 Hz
• 1 terahertz (1THz) 1 000 000 000 000 Hz

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4. Time period (T )

• Time period is the time taken for a source to
  produce one wave.
• time period 1
• frequency
• and
• frequency 1
• time period

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Question 1

• Calculate the frequency of a wave of time period
  8.0 seconds.
• f 1 / T
• 1 / 8
• frequency 0.125 hertz

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Question 2

• Calculate the time period of a wave of frequency
  50Hz.
• T 1 / f
• 1 / 50
• time period 0.020 second

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The wave equation

• speed frequency x wavelength
• v f x ?
• speed in metres per second (m/s)
• wavelength in metres (m)
• frequency in hertz (Hz)
• also f v ?
• and ? v f

v
?
f
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Question 1

• Calculate the speed of a water wave of wavelength
  3m and frequency 6Hz.
• v f x ?
• 6Hz x 3m
• speed 18 m/s

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Question 2

• Calculate the frequency of a wave in water of
  wavelength 2.0m if its speed is 16m/s.
• v f x ?
• becomes
• f v ?
• 16 m/s 2m
• frequency 8 Hz

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Question 3

• Calculate the wavelength of a sound wave in water
  of frequency 300Hz if its speed is 1500m/s.
• v f x ?
• becomes
• ? v f
• 1500 m/s 300 Hz
• wavelength 5 metres

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Question 4

• Calculate the speed of a wave that has a
  wavelength of 30m and time period 0.04s.
• f 1 / T
• 1 / 0.04s
• f 25 hertz
• v f x ?
• 25Hz x 30m
• speed 750 m/s

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Complete
Answers
v f ?
15 Hz 4 m
330 m/s 2 m
300 000 000 m/s 1 500 m
300 000 km/s 100 MHz
60 m/s
165 Hz
200 000 Hz
3 m
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Diffraction
TRIPLE ONLY

• Diffraction occurs when waves spread out after
  passing through a gap or round an obstacle.

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TRIPLE ONLY

• Diffraction becomes more significant when the
  size of the gap or obstacle is reduced compared
  with the wavelength of the wave.

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Choose appropriate words to fill in the gaps
below A wave transfers _______ without the
movement of _______ from one place to another.
In a __________ wave the particle ____________
are perpendicular to the direction of wave
travel. Frequency is equal to the number of waves
produced by a source in one _________. Time
period is equal to the ___________ of the
frequency. The speed of a wave in m/s is equal to
its __________ in metres multiplied by its
__________ in hertz.
energy
matter
transverse
vibrations
second
reciprocal
wavelength
frequency
WORD SELECTION
reciprocal
transverse
energy
frequency
wavelength
vibrations
second
matter
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Online Simulations

• Simple demonstration of longitudinal transverse
  waves - Freezeway.com
• Wave lab - shows simple transverse longitudinal
  waves with reflection causing a stationary wave -
  by eChalk
• Wave Effects - PhET - Make waves with a dripping
  faucet, audio speaker, or laser! Add a second
  source or a pair of slits to create an
  interference pattern. Also shows diffraction.
• Virtual Ripple Tank - falstad
• Fifty-Fifty Game on Wave Types - by KT -
  Microsoft WORD
• Simple transverse wave - netfirms
• Simple longitudinal wave - netfirms
• Simple wave comparision - amplitude, wavelength -
  7stones
• Fifty-Fifty Game on Wave Types - by KT -
  Microsoft WORD
• Wave on a String - PhET - Watch a string vibrate
  in slow motion. Wiggle the end of the string and
  make waves, or adjust the frequency and amplitude
  of an oscillator. Adjust the damping and tension.
  The end can be fixed, loose, or open.
• Vend diagram quiz comparing light and sound waves
  - eChalk
• BBC AQA GCSE Bitesize Revision
• What are waves
• Amplitude, wavelength and frequency
• Wave speed

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Properties of WavesNotes questions from pages 91
to 98
TRIPLE ONLY

1. (a) What is a wave? (b) Explain the difference
   between a transverse and longitudinal wave (see
   pages 91 and 92)
2. Define what is meant by (a) amplitude (b)
   wavelength (c) frequency and (d) time period.
   (see pages 92 and 93)
3. (a) State the wave equation. (b) Calculate the
   wavelength of a radio wave of frequency 10MHz,
   speed 300 000km/s.(see pages 93 and 94)
4. (a) What is wave diffraction? (b) Draw diagrams
   showing how diffraction is affected by the
   wavelength of a wave. (see page 97)
5. Answer the questions on page 98.
6. Verify that you can do all of the items listed in
   the end of chapter checklist on page 98.

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Properties of WavesNotes questions from pages 91
to 98
DOUBLE ONLY

1. (a) What is a wave? (b) Explain the difference
   between a transverse and longitudinal wave (see
   pages 91 and 92)
2. Define what is meant by (a) amplitude (b)
   wavelength (c) frequency and (d) time period.
   (see pages 92 and 93)
3. (a) State the wave equation. (b) Calculate the
   wavelength of a radio wave of frequency 10MHz,
   speed 300 000km/s. (see pages 93 and 94)
4. Answer questions 1, 3 and 4 on page 98