electromagnetic spectrum 2010

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Chapter12

Chapter12

Electromagnetic

Spectrum

Electromagnetic

Spectrum

The light waves that we studied in the last chapter are just one part of a much more extensive range known as

electromagnetic waves. All electromagnetic waves havecertain fundamental properties in common.

The light waves that we studied in the last chapter are just one part of a much more extensive range known as

electromagnetic waves. All electromagnetic waves havecertain fundamental properties in common.



contentscontents

Properties of ElectromagneticWaves

Applications of ElectromagneticWaves

Chapter Review

Properties of ElectromagneticWaves

Applications of ElectromagneticWaves

Chapter Review



electromagnetic spectrum



properties of electromagnetic waves


An electromagnetic wave is produced by the simultaneousvibration of electric and magnetic fields.

All electromagnetic waves

An electromagnetic wave is produced by the simultaneousvibration of electric and magnetic fields.

All electromagnetic waves

transfer energy from one placeto another

are transverse waves

travel through a vacuum withthe same high speed (speed of

light) at 3 x 108 m s-1

show wave properties likereflection and refraction

transfer energy from one placeto another

are transverse waves

travel through a vacuum withthe same high speed (speed of

light) at 3 x 108 m s-1

show wave properties likereflection and refraction





All electromagnetic waves obey the wave equation.All electromagnetic waves obey the wave equation.

v = f P



Components of electromagnetic spectrumComponents of electromagnetic spectrum

Speed in a vacuumSpeed in a vacuumis constantis constant

c = 3 x 10c = 3 x 1088 m sm s--11

Electromagnetic SpectrumElectromagnetic Spectrum

Gamma

rays X-rays Ultraviolet Visible light Infrared Microwave Radio wave

low

frequency

high

frequency

shortwavelength

longwavelength

Several km< 10-12 m

electromagnetic spectrumelectromagnetic spectrum

applications of electromagnetic waves




radio waveradio wave



is the longest EM wave in the electromagnetic spectrum

has wavelength of 10-1 to 105 m

is used in radio communication (LW, MW, SW and VHF)and television transmission (UHF and VHF) over longdistances

is the longest EM wave in the electromagnetic spectrum

has wavelength of 10-1 to 105 m

is used in radio communication (LW, MW, SW and VHF)and television transmission (UHF and VHF) over longdistances

television transmission is made possible

with the use of VHF and UHF radio waves

source: TV and radiotransmitters

detector: aerials of TV

and radio receivers

source: TV and radiotransmitters

detector: aerials of TV

and radio receivers



microwavemicrowave



is very similar to UHF radio waves

has wavelength of 10-3 to 10-1 m

is used in satellite communication and transmission,radar systems and microwave cooking

travels in straight line without losing much of its energy

is very similar to UHF radio waves


is used in satellite communication and transmission,radar systems and microwave cooking

travels in straight line without losing much of its energy

source: electronicdevices (klystrontubes)

detector: microwavereceivers

source: electronicdevices (klystrontubes)

detector: microwavereceivers

speed-monitoringradar

satellite station




applications of electromagnetic wavesinfra-red radiationinfra-red radiation

is the radiation beyond the red end of the visible spectrum


is used in remote control devices, intruder alarms, infra-red photography and radiant heaters

is the radiation beyond the red end of the visible spectrum


is used in remote control devices, intruder alarms, infra-red photography and radiant heaters

is emitted by objects withtemperature above 0 K;hotter objects more thancolder ones

source: warm bodies

detector: specialphotographic films,blackened thermometersand thermocouples

is emitted by objects withtemperature above 0 K;hotter objects more thancolder ones

source: warm bodies

detector: specialphotographic films,blackened thermometersand thermocouples an IR photograph



visible light visible light



can be seen by human eye

has wavelength of 4 x 10-7 to 7 x 10-7 m

can be seen by human eye

has wavelength of 4 x 10-7 to 7 x 10-7 m

is used in optical fibres,medical usage,telecommunications,chemical spectral analysisand photosynthesis

source: hot bodies, lasersand sun

detector: eyes, photographicfilm and photocells

is used in optical fibres,medical usage,telecommunications,chemical spectral analysisand photosynthesis

source: hot bodies, lasersand sun

detector: eyes, photographicfilm and photocells

laser surgery



ultra-violet radiationultra-violet radiation



is the radiation beyond the violet end of the visible spectrum


stimulates our bodies to produce vitamin D

is the radiation beyond the violet end of the visible spectrum


stimulates our bodies to produce vitamin D

is used in sunbeds,fluorescent tubes,sterilisation, forgerydetection and fluorescencein washing powders

source: sun, mercuryvapour and lamps

detector: photographic film,fluorescent screens, dyesand photocells

is used in sunbeds,fluorescent tubes,sterilisation, forgerydetection and fluorescencein washing powders

source: sun, mercuryvapour and lamps

detector: photographic film,fluorescent screens, dyesand photocells overexposure to UV radiation

can cause skin cancer



x-ray x-ray




is penetrating and can causedamage to tissues and organisms

is used in medical and dentaldiagnostic tools and engineeringapplications

source: x-ray tubes

detector: photographic film and

fluorescent screens


is penetrating and can causedamage to tissues and organisms

is used in medical and dentaldiagnostic tools and engineeringapplications

source: x-ray tubes

detector: photographic film and

fluorescent screens

x-ray photograph of hand



gamma ray gamma ray




is penetrating and can cause damage to living tissuesand organisms

is used in medical treatment and checking of welds,under controlled situations

source: cosmic rays, radioactive substances and nuclearreaction

detector: Geiger-Müller counters, bubble/cloud chambers

and photographic film


is penetrating and can cause damage to living tissuesand organisms

is used in medical treatment and checking of welds,under controlled situations

source: cosmic rays, radioactive substances and nuclearreaction

detector: Geiger-Müller counters, bubble/cloud chambers

and photographic film



Learning Outcomes

y state that all electromagnetic waves are transverse

waves that travel with the same speed in vacuo andstate the magnitude of this speed

y describe the main components of the electromagneticspectrum

y state examples of the use of the following components:

radio waves (e.g. radio and television communication)microwaves (e.g. microwave oven and satellitetelevision), infra-red (e.g. infra-red remote controllersand intruder alarms) light (e.g. optical fibres for medicaluses and telecommunications) ultra-violet (e.g. sun bedsand sterilisation) X-rays (e.g. radiological and

engineering applications) gamma rays (e.g. medicaltreatment)

y describe the effects of absorbing electromagnetic waves,e.g. heating, ionisation and damage to living cells andtissue.



http://imagine.gsfc.nasa.gov/docs/science/know_l1/emspectrum.html

http://www.lbl.gov/MicroWorlds/ALSTool/EMSpec/EMSpec2.html

http://science.hq.nasa.gov/kids/imagers/ems/ems.html

Website 1

Website 2

Website 3



ElectromagneticElectromagneticwaveswaves

c = 3 x 10c = 3 x 1088 m sm s--11

Transverse wavesTransverse waves

areare

with speed inwith speed in

vacuumvacuum

consist of consist of ComponentsComponents

Radio wavesRadio waves

MicrowavesMicrowaves

InfraInfra--red wavesred waves.

LightLight.

UltraUltra--violetviolet.

XX--raysrays.

Gamma raysGamma rays

ApplicationsApplications

Radio and television communicationRadio and television communication

Satellite television and telephoneSatellite television and telephone

Home electrical appliances, remoteHome electrical appliances, remotecontrols and intruder alarmscontrols and intruder alarms

Optical fibres in medical usage andOptical fibres in medical usage andtelecommuncationtelecommuncation

Sunbeds, fluorescent tubes andSunbeds, fluorescent tubes andsterilisationsterilisation

Medical use and engineeringMedical use and engineeringapplicationsapplications

Medical treatmentMedical treatment

electromagnetic spectrum 2010

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