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EDEXCEL IGCSE / CERTIFICATE IN PHYSICS 3-2 Using Waves (The Electromagnetic Spectrum). Content applying to Triple Science only is shown in red type on the next slide and is indicated on subsequent slides by ‘ TRIPLE ONLY ’. Edexcel IGCSE Physics pages 99 to 106. June 17 th 2012.

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edexcel igcse certificate in physics 3 2 using waves the electromagnetic spectrum

EDEXCEL IGCSE / CERTIFICATE IN PHYSICS 3-2Using Waves(The Electromagnetic Spectrum)

Content applying to Triple Science only is shown in red type on the next slide and is indicated on subsequent slides by ‘TRIPLE ONLY’

Edexcel IGCSE Physics pages 99 to 106

June 17th 2012

edexcel specification
Section 3: Waves

c) The electromagnetic spectrum

understand that light is part of a continuous electromagnetic spectrum which includes radio, microwave, infrared, visible, ultraviolet, x-ray and gamma ray radiations and that all these waves travel at the same speed in free space

identify the order of the electromagnetic spectrum in terms of decreasing wavelength and increasing frequency, including the colours of the visible spectrum

explain some of the uses of electromagnetic radiations, including:

• radio waves: broadcasting and communications

• microwaves: cooking and satellite transmissions

• infrared: heaters and night vision equipment

• visible light: optical fibres and photography

• ultraviolet: fluorescent lamps

• x-rays: observing the internal structure of objects and materials and medical applications

• gamma rays: sterilising food and medical equipment

understand the detrimental effects of excessive exposure of the human body to electromagnetic waves, including:

• microwaves: internal heating of body tissue

• infra-red: skin burns

• ultraviolet: damage to surface cells and blindness

• gamma rays: cancer, mutation.

and describe simple protective measures against the risks.

d) Light and sound

understand the difference between analogue and digital signals

describe the advantages of using digital signals rather than analogue signals

describe how digital signals can carry more information

Edexcel Specification

Red type: Triple Science Only

the electromagnetic spectrum
The Electromagnetic Spectrum

The electromagnetic spectrum is a continous spectrum of waves which includes the visible spectrum.

slide4
The electromagnetic spectrum is divided into seven bands which in order of decreasing wavelength are:

LONGEST WAVELENGTH

SHORTEST WAVELENGTH

RADIO WAVES

MICROWAVES

INFRA-RED

VISIBLE LIGHT

ULTRA-VIOLET

X-RAYS

GAMMA RAYS

slide5
Listing in order of decreasingfrequency and energy:

HIGHEST FREQUENCY

GREATEST ENERGY

LOWEST FREQUENCY

LEAST ENERGY

GAMMA RAYS

X-RAYS

ULTRA-VIOLET

VISIBLE LIGHT

INFRA-RED

MICROWAVES

RADIO WAVES

common properties
Common properties

All electromagnetic waves, including visible light have the following common properties:

1. They transfer energy

2. They are all transverse waves

3. They all travel at the same speed through

a vacuum (300 000 000 m/s)

4. They can all be reflected, refracted and diffracted**

Notes:

(a) 300 000 00 m/s is the same as 186 000 miles per second.

(b) Through air, light and the other waves travel at about the above speed but through denser substances (for example glass) the speed falls.

(c) According to Albert Einstein’s Theory of Relativity nothing can travel faster than the speed of light through a vacuum.

(d) ** Double Science students do not need to know about diffraction

question 1
Question 1

Calculate the wavelength of a radio wave in of frequency 100 MHz if its speed is 300 000 000 m/s.

wave speed (v)=frequency (f)xwavelength (λ)

becomes:

λ=v÷f

= 300 000 000 m/s ÷ 100 MHz

= 300 000 000 m/s ÷ 100 000 000 Hz

wavelength = 3.0 metres

question 2
Question 2

Calculate the frequency of a light wave of wavelength 0.000 7mm of speed 300 000 000 m/s.

v=fxλ

becomes:

f=v÷λ

= 300 000 000 m/s ÷ 0 000 7 mm

= 300 000 000 m/s ÷ 0 000 000 7 m

frequency = 429 000 000 000 000 Hz

(or = 4.29 x 1014 Hz)

complete
Complete:

Answers

highest frequency

longest wavelength

greatest energy

GAMMA

RADIO

GAMMA

X-RAYS

MICROWAVES

X-RAYS

ULTRAVIOLET

ULTRAVIOLET

INFRA-RED

VISIBLE LIGHT

VISIBLE LIGHT

VISIBLE LIGHT

INFRA-RED

ULTRAVIOLET

INFRA-RED

MICROWAVES

X-RAYS

MICROWAVES

RADIO

GAMMA

RADIO

lowest frequency

shortest wavelength

least energy

slide10

Choose appropriate words to fill in the gaps below:

The electromagnetic __________ is a group of waves that are divided into ________ bands.

Gamma rays have the ________ wavelength, highest frequency and ________. The rest of the spectrum, in order of increasing wavelength are:

x-rays, _________, visible light, infra-red, ___________ and radio waves.

All electromagnetic waves travel at the same _______ through a __________, 300 000 000 m/s.

spectrum

seven

shortest

energy

ultraviolet

microwaves

speed

vacuum

WORD SELECTION:

ultraviolet

shortest

energy

spectrum

vacuum

speed

seven

microwaves

slide12

RADIO

MICROWAVES

INFRA-RED

LIGHT

A radio transmitter

ULTRA-VIOLET

X-RAYS

GAMMA RAYS

Radio waves have the longest wavelengths of the electromagnetic spectrum, typically 100 metres.

uses of radio waves

MRI scanner and scan

Radio telescope

Uses of radio waves

Radio waves are used in:

  • radio and television communication
  • medicine with MRI scanners
  • astronomy to ‘see’ the centre of our galaxy
transmitting and receiving radio waves

transmitter

receiver

radio wave

Transmitting and receiving radio waves

Radio waves are emitted from a transmitter aerial when an alternating voltage is connected to the aerial. The radio wave emitted has the same frequency as the alternating voltage.

When these radio waves pass across a receiver aerial, they cause a tiny alternating voltage of the same frequency to occur in the aerial.

diffraction

TRIPLE ONLY

Diffraction out of a gap

Diffraction around an obstacle

Diffraction

Diffraction occurs when a wave spreads out from a gap or bends around an obstacle.

Diffraction is more significant with low frequency, long wavelength waves.

Diffraction results in the energy of the wave spreading out.

radio frequency bands
Radio frequency bands

The radio and microwave part of the electromagnetic spectrum is sub-divided into frequency bands. The uses of each band depends on its frequency range.

The higher the frequency:

  • The more information that can be carried – this can result in better quality sound and video or more channels.
  • The shorter their range – due to greater absorption by the atmosphere.
  • The less the signal spreads out – less diffraction – hills and large buildings also are more likely to stop the signal.

Higher frequency waves are less able to diffract around buildings and hills

wavebands
Wavebands

Microwaves

greater than 3 GHz (wavelength less than 10 cm)

Satellite TV Mobile phones

UHF (ultra-high frequency)

300 MHz – 3 GHz (wavelengths: 10 - 100 cm)

Terrestrial TV Mobile phones

VHF (very-high frequency)

30 MHz – 300 MHz (wavelengths: 1 - 10 m)

FM radio Emergency services Digital radio

HF (high frequency) also called ‘short wave’ or SW

3 MHz – 30 MHz (wavelengths: 10 – 100 m)

Amateur radio International radio (AM)

MF (medium frequency) also called ‘medium wave’ or MW

300 kHz – 3 MHz (wavelengths: 100 – 1000 m)

National radio (AM)

LF (low frequency) also called ‘long wave’ or LW

30 kHz – 300 MHz (wavelengths: 1 – 10 km)

International radio (AM)

VLF (very-low frequency)

less than 30 kHz (wavelengths more than 10 km)

Submarine communication

Note: 1 GHz = 1000 MHz; 1 MHz = 1000 kHz; 1 kHz = 1000 Hz

radio waves and the ionosphere
The ionosphere is a layer of gas in the upper atmosphere that reflects radio waves of frequencies less than about 30 MHz.

Radio waves can be reflected off the bottom of the ionosphere enabling them to travel great distances.

The ionosphere is stronger in summer than winter and so distant radio stations can be received better in summer.

Before the advent of satellites, using the ionosphere was one of the main ways of communicating around the world.

Radio waves and the ionosphere
slide20

RADIO

MICROWAVES

INFRA-RED

LIGHT

Microwave transmitter / receiver used for a mobile phone network.

ULTRA-VIOLET

X-RAYS

GAMMA RAYS

Microwaves have wavelengths of typically 10 cm.

uses of microwaves

Satellite television receiver

Cosmic Microwave Background Radiation

Uses of microwaves

Microwaves are used for:

  • cooking
  • mobile phone communication
  • satellite television
  • astronomy – finding out about the origin of the Universe
dangers of microwaves
Dangers of microwaves

Microwaves can cause internal heating of body tissue.

Microwave ovens contain metal shielding to prevent the microwaves from leaking out.

Some people believe that over use of mobile phones can lead to brain damage.

infra red radiation

An infra-red or thermal image.

RED = hot

BLUE = cold

Despite appearances this heater is giving off mostly invisible infra-red radiation.

Infra-red radiation
slide24

RADIO

MICROWAVES

INFRA-RED

LIGHT

ULTRA-VIOLET

X-RAYS

Infra-red photograph.

brighter = hotter

GAMMA RAYS

Infra-red waves have wavelengths of typically a millionth of a metre (1 micrometre)

They are emitted by all objects. The hotter the object, the more infra-red radiation is emitted.

uses of infra red
Uses of infra-red

Infra-red waves are used:

  • to cook food
  • by remote controls
  • in communication systems using optical fibres
  • to detect intruders in burglar alarms
  • in ‘night sights’
  • in astronomy to see behind gas clouds
slide26

Choose appropriate words to fill in the gaps below:

Infra-red radiation has a _________ wavelength than visible light and is _________ by all objects. The higher the ___________ of an object the greater is the amount of IR radiation emitted.

Microwaves have wavelengths of a few ___________ and are used for ________ and communication.

Radio waves have the longest wavelengths but the ________ frequencies of the electromagnetic spectrum. Radio waves are used to study the centre of our _________.

longer

emitted

temperature

centimetres

cooking

lowest

galaxy

WORD SELECTION:

emitted

lowest

galaxy

cooking

temperature

longer

centimetres

slide28
Visible light is emitted from hot objects like the Sun.

Visible light has wavelengths ranging from:

0.000 000 4m (violet)

to

0.000 000 7m (red).

RADIO

RED

MICROWAVES

ORANGE

INFRA-RED

YELLOW

LIGHT

GREEN

ULTRA-VIOLET

BLUE

X-RAYS

INDIGO

GAMMA RAYS

VIOLET

White light can be split into the colour spectrum using a prism or with water.

uses of visible light
Uses of visible light

Visible light is used:

  • for sight
  • in photography
  • in optical fibres
  • in photosynthesis
ultraviolet
Ultraviolet

Security markings show up under ultraviolet light

Ultraviolet emitted by the Sun

Fluorescent lamps and energy efficient bulbs work using uv

slide31
Ultraviolet has a wavelength of typically of a ten millionth of a metre.

UV is produced from very hot objects like the Sun or from special electrical tubes.

Most of the Sun’s ultraviolet radiation is absorbed by the Ozone layer in the upper part of the Earth’s atmosphere.

UV is also stopped by glass.

RADIO

MICROWAVES

INFRA-RED

LIGHT

ULTRA-VIOLET

X-RAYS

GAMMA RAYS

uses of ultraviolet
Uses of ultraviolet

Ultraviolet is used in:

Fluorescent lamps including energy efficient light bulbs

Security devices

Dentistry

Pest control

Astronomy

A bird appears on many Visa credit cards when held under a UV light source

Ultraviolet light used in cosmetic dentistry

‘zapper’ attracts insects using uv

safety with ultraviolet
Safety with ultraviolet

The Sun’s ultraviolet light is responsible for sun tan.

1

wear a hat

2

sunglasses with UV protection

3

cover up when the Sun is strongest

longer shorts offer protection

4

5

use a high sun protection factor sunscreen – reapply after swimming

Too much exposure to UV can cause blindness and skin cancer.

x rays
X-rays

X-ray photographs

Exploding stars emit X-rays

slide35
X-rays have wavelengths of typically a billionth of a metre.

They are produced from X-ray tubes that use very high voltage (typically one hundred thousand volts).

They are very penetrating and are only stopped by several centimetres of lead.

RADIO

MICROWAVES

INFRA-RED

LIGHT

ULTRA-VIOLET

X-RAYS

GAMMA RAYS

uses of x rays
Uses of X-rays

X-rays are used in:

X-ray photographs

Airport security

Cancer treatment

Astronomy

taking an x ray radiograph
Taking an X-ray (radiograph)

X-rays pass through soft tissue but are absorbed by bones.

X-rays are directed onto the patient from the X-ray tube.

A light proof cassette containing a photographic film is placed on the other side of the patient.

A patient being prepared for a radiograph

slide38
When the X-ray tube is switched on, the X-rays pass through the patient’s body leaving a ‘shadow’ image on the film showing the bones.

When the film is developed the parts exposed by the X-rays are darker than the other parts.

The bones show up as lighter regions on the radiograph.

A chest X-ray

gamma rays
Gamma Rays

Gamma rays are given off by nuclear explosions

Gamma rays are emitted from material falling into black holes

gamma rays40
Gamma Rays

Gamma rays have the shortest wavelengths of the electromagnetic spectrum, typically a millionth millionth of a metre.

They are emitted by radioactive substances.

They are very penetrating and are only stopped by several centimetres of lead.

RADIO

MICROWAVES

INFRA-RED

LIGHT

ULTRA-VIOLET

X-RAYS

GAMMA RAYS

uses of gamma rays
Uses of gamma rays

Gamma rays are used:

to kill cancer cells

to kill harmful bacteria in food

to sterilise surgical instruments

Gamma rays being used to treat cancer

safety with gamma and x rays
Safety with gamma and X-rays

Too much exposure to gamma rays or X-rays is dangerous.

High doses kill living cells. Low doses cause cell mutation and cancerous growth.

Workers who use equipment producing gamma or X-rays wear a film badge called a dosemeter. The film in the badge darkens if the person receives a too high dosage of radiation.

a dosemeter

slide43

Choose appropriate words to fill in the gaps below:

Gamma and X-rays are the most _________ radiations of the electromagnetic spectrum. Both can cause cell _________ and cancerous growth although both can also be used to treat ________.

Both require several centimetres of ______ to be stopped.

X-rays are absorbed by ______ allowing the production of radiographs.

Gamma rays are used to kill _________ in food and to _________ medical instruments.

dangerous

mutation

cancer

lead

bones

bacteria

sterilise

WORD SELECTION:

bones

mutation

cancer

bacteria

lead

dangerous

sterilise

analogue and digital signals

TRIPLE ONLY

Analogue and digital signals

Communication signals may be analogue or digital.

Analogue signals vary continuously in amplitude between zero and some maximum level.

Digital signals only have two voltage levels, for example +5V and 0V.

advantages of using digital signals

TRIPLE ONLY

Regenerator

‘Noisy’ pulse in

‘Clean’ pulse out

Advantages of using digital signals
  • Less interference than with analogue signals.

Interference causes a hissing noise with analogue radio. This does not happen with digital signals because regenerator circuits are used to clean ‘noisy’ pulses. So a digital signal has a higher quality than an analogue one.

slide48

TRIPLE ONLY

2. Much more information can be sent.

Digital pulses can be made very short so more pulses can be carried each second. Different signals can be sent together by a process called multiplexing.

3. Digital signals are easily processed by computers.

Computers are digital devices!

online simulations
Sequential Puzzle on EM Spectrum Wavelength order- by KT - Microsoft WORD

Sequential Puzzle on EM Spectrum Frequency order- by KT - Microsoft WORD

Hidden Pairs Game on EM Spectrum Uses - by KT - Microsoft WORD

Electromagnetic Spectrum bounce quiz - eChalk

Radio Waves & Electromagnetic Fields - PhET - Broadcast radio waves from KPhET. Wiggle the transmitter electron manually or have it oscillate automatically. Display the field as a curve or vectors. The strip chart shows the electron positions at the transmitter and at the receiver.

Microwaves - PhET - How do microwaves heat up your coffee? Adjust the frequency and amplitude of microwaves. Watch water molecules rotating and bouncing around. View the microwave field as a wave, a single line of vectors, or the entire field.

Thermal Camera Pictures - falstad

The Greenhouse Effect - PhET - Just how do greenhouse gases change the climate? Select the level of atmospheric greenhouse gases during an ice age, in the year 1750, today, or some time in the future and see how the Earth's temperature changes. Add clouds or panes of glass.

Online Simulations

Making X-rays - Colorado

X-rays - Fluoroscope demo - Colorado

Fibre optic reflection - NTNU

BBC AQA GCSE Bitesize Revision:

What is a spectrum

The electromagnetic spectrum - table

Radio waves

Microwaves

UV & IR

Gamma & X-rays

Hazards of radiation

Optical fibres

Analogue & digital signals

Comaparing analogue & digital

using waves notes questions from pages 99 to 106

TRIPLE ONLY

Using WavesNotes questions from pages 99 to 106
  • Copy the table on page 106.
  • Give five common properties of all members of the electromagnetic spectrum. (see page 99)
  • List the colours of the visible spectrum in order of increasing wavelength. (see page 102)
  • State the hazards of (a) microwaves; (b) ultra-violet; (c) X-rays and gamma rays. (see pages 101 to 103)
  • (a) Explain the difference between analogue and digital signals. (b) What are the advantages of using digital signals? (see pages 104 and 105)
  • Answer the questions on page 106.
  • Verify that you can do all of the items listed in the end of chapter checklist on page 106.
using waves notes questions from pages 99 to 10651

DOUBLE SCIENCE ONLY

Using WavesNotes questions from pages 99 to 106
  • Copy the table on page 106.
  • Give five common properties of all members of the electromagnetic spectrum. (see page 99)
  • List the colours of the visible spectrum in order of increasing wavelength. (see page 102)
  • State the hazards of (a) microwaves; (b) ultra-violet; (c) X-rays and gamma rays. (see pages 101 to 103)
  • Answer questions 1 and 2 on page 106.