p6 – the wave model of radiation. what creates a wave? must: recall that waves transfer energy...

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


• EG Peak to Peak, Trough to Trough

Wavelength


• EG Peak to Peak, Trough to Trough

• Measured in metres (m)

Frequency

Frequency

• How often waves come along

Frequency


• EG Number of total wave per second

Frequency


• Number of total waves per second

• Measured in Hertz (Hz)

Amplitude

Amplitude

• The size of a Wave

Amplitude


• The Maximum Displacement from the Baseline

Amplitude


• 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


(metres per second) (hertz) (metre)

The Wave Equation



m/s Hz m

The Wave Equation



m/s Hz m

Also written as v = fλ

How do Sound Waves Change?


• Low Frequency = Long Wavelength



• Low pitch Sounds




• High Frequency = Short Wavelength




• 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?


• Refraction is caused when waves change medium ( The Material that they are travelling through)


• 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?


When Light moves from AIR to GLASS it slows 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:


Be Reflected (Echo)


Be Reflected (Echo)

Be Refracted – passing through materials of different density


Be Reflected (Echo)


Be Diffracted – Spread out as they pass through a gap

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


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?


• Ultraviolet (UV)



• X-Rays



• X-Rays

• Gamma Rays

Why are these Radiations Harmful?


Shorter Wavelengths


Shorter Wavelengths

Higher Frequency


Shorter Wavelengths

Higher Frequency

More energy in each Photon


Shorter Wavelengths

Higher Frequency

More energy in each Photon

IONISING Radiation - Causes atoms to break apart

How can we protect Ourselves from Harmful Radiations?


• Avoid them


• 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


• All objects give off some infrared

Infra Red



• Most solids absorb infrared, causing temperature to rise

Infra Red



• 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


• UHF/VHF Radio waves and some Microwaves pass through the Atmosphere with very little absorption

Microwaves and Radio Waves


• 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

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?


• 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 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


• It is Demodulated (the RF carrier is removed)

Reciever


• 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


• Digital signals have only 2 variations – ‘On’ or ‘Off’

Analogue vs Digital


• Digital signals have only 2 variations – ‘On’ or ‘Off’

• These Digital signals are Binary Code – 1’s and 0’s

Advantages of Digital


Digital can be used by microprocessors (computers)



Digital can carry more information every second than analogue



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

p6 – the wave model of radiation. what creates a wave? must: recall that waves transfer energy...

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