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 Equation COULD: 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 Which distance A, B, C or D is the Wavelength of the Microwave? _____ (1) 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 m/s Hz m (metres per second) (hertz) (metre) m/s Hz m

The Wave Equation wave speed = frequency x wavelength m/s Hz m (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 wave SHOULD: be able to measure the critical angle for light COULD: 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 Wave Sound Waves can:

Sound is a Wave Sound Waves can: Be Reflected (Echo)

Sound is a Wave Sound Waves can: Be Reflected (Echo) Be Refracted – passing through materials of different density

Sound is a Wave Sound 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 Wave Sound 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

There is a bright spot in the centre of this shadow made by a tiny ball bearing. The shadow of a razor blade using laser light.

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 Slows down – to around 200,000 km/s 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 radiation SHOULD: 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 absorption SHOULD: be able to describe factors that that affect absorption COULD: 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

Microwave signal passes through Microwave signal stopped 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 RF SHOULD: be able to describe the differences in AM and FM COULD: 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 Draw a diagram to compare the differences in transmission and reception of Analogue and Digital Signals (page 255) Complete Questions 1, 2 and 3 – Page 254