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P6 – The Wave model of Radiation
What creates a Wave?
• MUST: recall that waves transfer energy
• SHOULD: be able to describe the form of longitudinal and transverse waves and give examples
• COULD: Be able to explain the form of a wave using key terms
Longitudinal Waves• These are compression Waves
• Energy compacts particles closer together and this is passed through the medium (the material)
• The energy displaces the material in the direction of the wave
• EG SOUND WAVES
• Example - SOUND waves
Longitudinal Soundwave
Task
• AP6.4
Transverse Waves
• “Side to Side” waves
• The energy displaces the material at right angles to the direction of the wave
• Water Waves and ALL electromagnetic radiation (including light) are Transverse Waves
Transverse Wave
Tasks
• Activity AP6.3
What can Change about a Wave?
MUST: Know the terms Wavelength, Frequency and Amplitude
SHOULD: Be able to use the Wave EquationCOULD: Be able to explain changes in wave
patterns using the wave equation
What types of Wave are there?
Name the two different types of wave
Give examples of each type of them
Wave Terms
Wavelength
Wavelength
• The length of whole wave Cycle
Wavelength
• The length of whole wave Cycle
• EG Peak to Peak, Trough to Trough
Wavelength
• The length of whole wave Cycle
• EG Peak to Peak, Trough to Trough
• Measured in metres (m)
Frequency
Frequency
• How often waves come along
Frequency
• How often waves come along
• EG Number of total wave per second
Frequency
• How often waves come along
• Number of total waves per second
• Measured in Hertz (Hz)
Amplitude
Amplitude
• The size of a Wave
Amplitude
• The size of a Wave
• The Maximum Displacement from the Baseline
Amplitude
• The size of a Wave
• The Maximum Displacement from the Baseline
• Measure from Base to Peak or Base to Trough
Simple Examination Question(b) This graph shows a microwave
i) Which distance A, B, C or D is the Wavelength of the Microwave? _____ (1)
ii) Which distance A, B, C or D is the Amplitude of the Microwave? _____ (1)
Activity AP6.6
The Wave Equation
The Wave Equation
wave speed = frequency x wavelength
The Wave Equation
wave speed = frequency x wavelength
(metres per second) (hertz) (metre)
The Wave Equation
wave speed = frequency x wavelength
(metres per second) (hertz) (metre)
m/s Hz m
The Wave Equation
wave speed = frequency x wavelength
(metres per second) (hertz) (metre)
m/s Hz m
Also written as v = fλ
How do Sound Waves Change?
How do Sound Waves Change?
• Low Frequency = Long Wavelength
How do Sound Waves Change?
• Low Frequency = Long Wavelength
• Low pitch Sounds
How do Sound Waves Change?
• Low Frequency = Long Wavelength
• Low pitch Sounds
• High Frequency = Short Wavelength
How do Sound Waves Change?
• Low Frequency = Long Wavelength
• Low pitch Sounds
• High Frequency = Short Wavelength
• High pitch Sounds
Tasks
• Activity AP6.8 – 10 minutes
• Calculations using the Wave Equation• Check your answer to question 4b - Is there anything wrong
with this answer?
• Text Book – Pages 236, 237
• Questions 1 – 6
What can happen to waves in a medium?
MUST: know the terms reflection, refraction, diffraction and interference
SHOULD: be able to explain these wave effects
COULD: use wave effects to explain common phenomena
Starter
Tasks
• Watch the demonstrations
• Complete the worksheet (AP6.11) from your observations
Definitions
Definitions
• Reflection – When waves bounce off something
Definitions
• Reflection – When waves bounce off something
• Refraction – As waves change medium they may slow down or speed up – This can create a change in course/direction
Refraction
Definitions
Definitions
• Diffraction – After waves pass through a gap or pass a barrier, they spread out.
Definitions
• Diffraction – After waves pass through a gap or pass a barrier, they spread out.
• Interference – When waves meet they can reinforce or deconstruct
Tasks
• Pages 238, 239
• Copy and label the Wave Diagrams of Reflection, Diffraction and Interference
• Include an explanation of what is happening
Wave Effects
MUST: recall the wave effects
SHOULD: be able to describe how waves can be refracted
COULD: be able to explain the refraction effect
What are the Wave Effects?
Reflection
Refraction
Interference
Diffraction
How does Refraction occur?
How does Refraction occur?
• Refraction is caused when waves change medium ( The Material that they are travelling through)
How does Refraction occur?
• Refraction is caused when waves change medium ( The Material that they are travelling through)
• This is because the waves CHANGE SPEED as they change Medium
Speed up or Slow Down?
Speed up or Slow Down?
When Light moves from AIR to GLASS it slows down
Speed up or Slow Down?
When Light moves from AIR to GLASS it slows down
When Light Moves from GLASS to AIR it speeds up
Tasks
• Page 240 – Copy and Label diagrams of Light Rays - Reflection and Refraction
• Activity AP6.17
Plenary
• Activity Sheet AP6.18
Is light really a Wave?
MUST: recall evidence for light being a waveSHOULD: be able to measure the critical
angle for lightCOULD: be able to explain the wave effects of
light
What are these Wave Effects?
A. B.
C. D.
Sound Waves?
Is sound a wave?
Give at least three reasons for your answer
Sound is a Wave
Sound is a WaveSound Waves can:
Sound is a WaveSound Waves can:
Be Reflected (Echo)
Sound is a WaveSound Waves can:
Be Reflected (Echo)
Be Refracted – passing through materials of different density
Sound is a WaveSound Waves can:
Be Reflected (Echo)
Be Refracted – passing through materials of different density
Be Diffracted – Spread out as they pass through a gap
Sound is a WaveSound Waves can:Be Reflected (Echo)
Be Refracted – passing through materials of different density
Be Diffracted – Spread out as they pass through a gap
Undergo Interference
Is Light a Wave?
Task
• Activity AP6.19
• Light on Trial
• Answer the Questions on the Properties of Light – Could this be done by particles and / or by waves
The shadow of a razor blade using laser light
The shadow of a needle
The shadow of a razor blade using laser light.
There is a bright spot in the centre of this
shadow made by a tiny ball bearing.
Diffraction of waves by a
barrier
The light from a laser
shone through a single
narrow slit
White light through a
narrow slit gives coloured
fringes.
The pattern formed by
light passing through two
narrow slits
Interference of water
waves
Reflection of Light
Carry out Practical Activity AP6.20
Find the Critical Angle of Glass
Critical Angle - Glass
Critical Angles
The Angle at which light is totally internally reflected within a substance
For glass this is around 42 degrees
Total Internal Reflection
Diamond
Critical Angle - Diamond
Refractive index of Gemstones
http://www.allaboutgemstones.com/gemstone_refractive_index.html
Plenary
• Can you TIR in water?
What is the Electromagnetic Spectrum?
MUST: recall the radiations that make up the electromagnetic spectrum
SHOULD: be able to describe how Frequency and Wavelength change through the Spectrum
COULD: be able to explain how the changes in Frequency and Wavelength relate to the Wave
Equation
Starter• What are the 7 colours of the Rainbow?
• What is the Speed of Light in air?
• What happens to the speed of light in Water?
• What happens to the speed of light in glass?
Starter• What are the 7 colours of the Rainbow?
Red, Orange, Yellow, Green Blue, Indigo, Violet
• What is the Speed of Light in air?
300,000 km/s
• What happens to the speed of light in Water?
Slows down – to around 230,000 km/s
• What happens to the speed of light in glass?
Slows down – to around 200,000 km/s
What is Light?
• An electromagnetic wave
• Contains a range of Frequencies and Wavelengths that make up the different colours of light (ROY G BIV)
• When mixed together they are seen as white light
Making a Spectrum
Task
• AP6.24
• Match the diagrams that represent each form of radiation to the Electromagnetic Spectrum
• Give examples of each of the uses (Page 245 in Text Book)
• Page 244
• Questions 1, 2, 3 and 4
Task
• Complete Activity Sheet AP6.23a
• You WILL need a Scientific Calculator for the Calculations (GET ONE FOR THE EXAM)
• If you can’t work out the answers using the Wave Equation, try to predict the values.
Plenary
• Electromagnetic Spectrum
The Risky Side of the Rainbow?
MUST: recall which radiations are the most harmful
SHOULD: recall how these radiations can be used and detected
COULD: be able to explain why these radiations are more harmful
Starter
• List all the different types of radiation in the Electromagnetic Spectrum
• Start at Radio Waves and go in order of Increasing Frequency / Decreasing Wavelength
• Give a use of each one of the radiation types
Which radiations are Risky?
Which radiations are Risky?
• Ultraviolet (UV)
Which radiations are Risky?
• Ultraviolet (UV)
• X-Rays
Which radiations are Risky?
• Ultraviolet (UV)
• X-Rays
• Gamma Rays
Why are these Radiations Harmful?
Why are these Radiations Harmful?
Shorter Wavelengths
Why are these Radiations Harmful?
Shorter Wavelengths
Higher Frequency
Why are these Radiations Harmful?
Shorter Wavelengths
Higher Frequency
More energy in each Photon
Why are these Radiations Harmful?
Shorter Wavelengths
Higher Frequency
More energy in each Photon
IONISING Radiation - Causes atoms to break apart
How can we protect Ourselves from Harmful Radiations?
How can we protect Ourselves from Harmful Radiations?
• Avoid them
How can we protect Ourselves from Harmful Radiations?
• Avoid them
• Use Materials that Block or Absorb the radiations
Tasks
• Page 247
• Copy and Define Key Words – Ultraviolet, Ionising Radiation, X-Rays, Gamma Rays
• Answer Questions 1, 2 and 3
Tasks
• Activity AP6.29
• Uses of X – Rays
• Activity AP6.28
• X – Ray film badge
How is Infrared radiation useful to us?
ALL MUST: Recall the effects of Infrared radiationSHOULD: Be able to explain the uses of infrared radiation
COULD: Be able to describe and explain the changing frequency and wavelength of IR as it relates to different
temperatures
Starter
• List the Seven colours of the spectrum in order from Lowest Frequency/longest wavelength to highest/shortest
• On either end of the spectrum, add the invisible radiations found immediately beyond these
• List a couple of uses of these invisible radiations
Infra Red
Infra Red
• Beneath the Visible Spectrum, beyond red
Infra Red
• Beneath the Visible Spectrum, beyond red
• All objects give off some infrared
Infra Red
• Beneath the Visible Spectrum, beyond red
• All objects give off some infrared
• Most solids absorb infrared, causing temperature to rise
Infra Red
• Beneath the Visible Spectrum, beyond red
• All objects give off some infrared
• Most solids absorb infrared, causing temperature to rise
• Only Higher Frequency IR can pass through glass and clear Plastics. Other frequencies are absorbed or reflected – See Greenhouse Effect
Infrared Radiation
Plenary
• Practice examination question
How are Microwaves useful?MUST: recall microwave and radiowave are
transmission and absorptionSHOULD: be able to describe factors that
that affect absorptionCOULD: be able to explain the importance
of the use of different radiations
Starter
• Question sheet – X Rays
• Radio Waves?
Microwaves and Radiowaves
Microwaves and Radiowaves
• Primary use is for Communication (TV, Satellite, Mobile phones, Radio, etc)
Microwaves and Radio Waves
• Primary use is for Communication (TV, Satellite, Mobile phones, Radio, etc)
• UHF/VHF Radio waves and some Microwaves pass through the Atmosphere with very little absorption
Microwaves and Radio Waves
• Primary use is for Communication (TV, Satellite, Mobile phones, Radio, etc)
• UHF/VHF Radio waves and some Microwaves pass through the Atmosphere with very little absorption
• Medium and Long Wave radiowaves are reflected off the Atmosphere
• Of these, Microwaves have the shortest wavelength, so are diffracted the least
What stops a Microwave?
• Demo
What Stops a Microwave?
Microwave signal passes through
Microwave signal stopped
What stops a Microwave?
• Microwaves transmit through:
• The Air / Atmosphere
• Dry, Non Metallic Solids
• Microwaves are stopped by:
• Metals
• Water / Moisture
Satellite TV
• What happens to Satellite TV in a Very Heavy Thunderstorm?
• Why?
Tasks
• Activity AP6.34
• Sketch the “Atmospheric Window” Graph into your Book.
• Note which radiations transmit strongly through our atmosphere and those that don’t
• Answer Questions 1 – 5
• Extension – Text Book – Page 251 – Questions 6, 7 and 8
Is there anybody out there?
• If you want to find signs of Life on Other planets and in Other Galaxies, what types of Radiation would you look for or use to try and send messages with?
• Why?
Telescopes
Keck Telescope
Keck Telescope
Arecibo Radio Telescope
Pulsar Telescope
Looking into Space
• Video Clip
Plenary
• Question Sheet
How does a Radio work?
MUST: recall the terms FM, AM and RFSHOULD: be able to describe the differences in
AM and FMCOULD: Be able to explain the difference between
AM and FM and how they are used
Starter
• Microwaves or Microwaves?
• Worksheet Questions
Beacon fires
• Beacon fires have been used
throughout history to communicate
warnings (the Spanish Armada) and
as celebrations (Queen Elizabeth’s
Silver Jubilee).
• Are beacon fires a digital signalling
device or an analogue device?
• What problems might there be in
communicating with signal fires?
Smoke signals
• Analogue or digital?
• What problems might there be using
smoke signals?
Semaphore
• Analogue or digital?
International flag signal code used by shipping
Analogue or digital?
Morse code
This is not just a digital signalling
system but a binary tool. There are just
two symbols used: a dot and a dash.
Radio waves
Radio signals are broadcast by modulating a
radio wave. Today many signals are broadcast
using an analogue system, but more and more
signals are broadcast in digital form.
Fax machines
These use a binary digital
system to transmit
information: everything is
transmitted as a stream of
0s and 1s down telephone
cables.
Mobile phones
A digital binary device
again: this time, the signal
is transmitted in the form
of microwave radiation
through the air.
How does a Radio work?
• Page 252
• Draw a Flow Diagram to show the stages in the process from Sound at the Transmission end to Sound at the Listener’s Radio
• Copy and Define Key Words – Carrier, Amplitude Modulation, Frequency Modulation, Noise
• Text Book – Page 253 – Questions 1 - 3
How does a Radio Work?
How does a Radio Work?
• A Radiowave (RF Wave) is created
How does a Radio Work?
• A Radiowave (RF Wave) is created
• A Modulator Combines it with a SOUND wave
How does a Radio Work?
• A Radiowave (RF Wave) is created
• A Modulator Combines it with a SOUND wave
• The Sound wave creates a Pattern in the repeating RF Wave
How does a Radio Work?
• A Radiowave (RF Wave) is created
• A Modulator Combines it with a SOUND wave
• The Sound wave creates a Pattern in the repeating RF Wave
• The Modulated RF carrier waves are Transmitted
Reciever
Reciever
• The Modulated RF wave is Received
Reciever
• The Modulated RF wave is Received
• It is Demodulated (the RF carrier is removed)
Reciever
• The Modulated RF wave is Received
• It is Demodulated (the RF carrier is removed)
• The Electrical signal is amplified and creates the sound wave from the speakers
AM or FM?
• AM – Amplitude Modulation
• FM – Frequency Modulation
AM
• Amplitude modulation.
• The amplitude changes from large to small to large again to copy the changes in the sound wave being carried by the radio wave.
• The frequency does not change.
FM
• Frequency modulation.
• The frequency changes from high to low to high again to copy those same changes in the sound wave being carried by the radio wave.
• The amplitude does not change
Tasks
• Text Book – Page 253 – Questions 1 - 3
Plenary
• Worksheet Questions
• Adding information to waves
FM and Digital
MUST: recall the differences between AM, FM and Digital Radio signals
SHOULD: be able to explain advantages of FM and Digital Signals
COULD: be able to explain the differences between Analogue and Digital Signals
Starter
• Worksheet questions – AM / FM
• Radio Signals
FM vs AM
FM vs AM
Noise creates extra unwanted variations in amplitude
FM vs AM
Noise creates extra unwanted variations in amplitude
FM picks up less electrical interference (noise) than AM signals
Analogue vs Digital
Powerpoint
Demonstration
How is Analogue converted to Digital?
• Page 254 - Section J
Analogue vs Digital
Analogue vs Digital
• Analogue signals have continuous variation
Analogue vs Digital
• Analogue signals have continuous variation
• Digital signals have only 2 variations – ‘On’ or ‘Off’
Analogue vs Digital
• Analogue signals have continuous variation
• Digital signals have only 2 variations – ‘On’ or ‘Off’
• These Digital signals are Binary Code – 1’s and 0’s
Advantages of Digital
Advantages of Digital
Digital can be used by microprocessors (computers)
Advantages of Digital
Digital can be used by microprocessors (computers)
Digital can carry more information every second than analogue
Advantages of Digital
Digital can be used by microprocessors (computers)
Digital can carry more information every second than analogue
Digital can be delivered with no loss of quality. ‘Noise’ can be cleaned up.
Tasks
1. Draw a diagram to compare the differences in transmission and reception of Analogue and Digital Signals (page 255)
2. Complete Questions 1, 2 and 3 – Page 254