gcse science a physics 1 waves learning outcomes characterise waves in terms of their wavelength,...
TRANSCRIPT
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WavesWavesLearning Outcomes
• Characterise waves in terms of their wavelength, frequency, speed and amplitude.
• Distinguish between the different regions of the electromagnetic spectrum. Including their uses and dangers
• Appreciate that all the regions of the electromagnetic spectrum transfer information and energy.
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WavesWaves
Key Words:
• Electromagnetic Spectrum: The collective name for radio waves, microwaves, infrared etc...
• Wavelength: The “length” of one complete wave.
• Frequency: The number of complete waves passing a point per second.
• Amplitude: The height of the wave
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WavesWaves
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Waves
Start
Consider a wave on the wave machine (click start to begin)…
Stop the motion by clicking again anywhere on the page – can you see that there is a repeat in the pattern?
Using the ruler, measure the distance between the pattern starting and the repeat starting.
You should find that the length is about 7.7cm – this is the WAVELENGTH of the wave.
Show/ hide ruler
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Waves
Using the ruler, measure the distance between the central starting point (the blue dotted line) and the maximum distance moved by any particle.
Start
In the same way….
Stop the motion by clicking again anywhere on the page. You should notice that the individual parts of the wave move between two extremes.
You should find that the length is about 1.3cm – this is the AMPLITUDE of the wave.
Show/ hide ruler
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Waves
wavelength (m)amplitude (m)
crest trough
Label the diagram by moving the terms from the box below to their correct positions on the diagram.
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Waves
Wavelength (m) =
amplitude (m) =
1. Number of complete waves =
30m
2m
Wavelength (m) =
amplitude (m) =
2. Number of complete waves =
2m
0.5m
Wavelength (cm) =
amplitude (cm) =
3. Number of complete waves =
4.5cm
3cm
Answers
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Waves
Wavelength (m) =
amplitude (m) =
1. Number of complete waves =
30m
2m
Wavelength (m) =
amplitude (m) =
2. Number of complete waves =
2m
0.5m
Wavelength (cm) =
amplitude (cm) =
3. Number of complete waves =
4.5cm
3cm
3
30/3 = 10
2/2 = 1
6
2/6 = 0.3
0.5/2 = 0.25
1.5
4.5/1.5 = 3
3/2 = 1.5
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WavesThe Electromagnetic Spectrum
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WavesThe Electromagnetic Spectrum
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WavesThe Electromagnetic Spectrum
All EM Waves;• Travel at the speed of light (3x108m/s).• All carry Energy and Information.
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WavesThe Electromagnetic Spectrum
Uses Dangers
Used for communicating over vast distances
Transmitting TV and radio programmes
Radio
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WavesThe Electromagnetic Spectrum
Uses Dangers
Heating food. Some people are concerned about possible health risks
with the signals from mobile phones. In particular; long term exposure for childrenMobile phone signals
Microwave
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WavesWaves and communication
Satellite Communications• Geostationary orbit: Satellite orbits above the same point on the Earth at all times• The satellite takes 24 hours to orbit the Earth.• Satellites (mainly) use microwaves to communicate with base stations on Earth.
Fibre Optic Cable• Use infrared to send information down special cable using “total internal
reflection”• Speed of infrared radiation in the cable is 2x108m/s
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WavesThe Electromagnetic Spectrum
Uses Dangers
Heating food (toasters, grills)
Can cause skin burnsHeating people (patio warmers)
Remote controls
Fibre-optic cables (broadband)
Infrared
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WavesThe Electromagnetic Spectrum
Uses Dangers
Seeing
Can cause eye damage if very bright
Communication
CD-players and Blu-Ray
Lasers
Visible
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WavesThe Electromagnetic Spectrum
Uses Dangers
Used to sterilise water. Can ionise skin cells causing sunburn and skin cancer.Detected forged notes
Sick Raves Can cause eye damage (cataracts)
Ultraviolet
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WavesThe Electromagnetic Spectrum
Uses Dangers
Medical Imaging X-rays are highly ionising, and can cause cancer anywhere
within the body.Detected by some space telescopes.
X-rays
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WavesThe Electromagnetic Spectrum
Uses Dangers
Used for medical imaging Gamma Rays are highly ionising, and can cause cancer
anywhere within the body.Sterilisation of medical equipment
Chemotherapy
Gamma rays
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Waves
Plenary – What if?
What if we had never discovered EM – waves (excluding visible light)?
Write an account of what the world would be like in the absence of these waves. How would it be different, and what would be our main challenges as human beings?