ELECTROMAGNETIC SPECTRUM

Name: ________________

Class: _________________

Index: ________________

At the end of the topic you should be able to… state that all electromagnetic waves are transverse waves that

travel with the same high speed in vacuo and state the magnitude of this speed

describe the main components of the electromagnetic spectrum discuss the role of the following components in the stated

applications:1. radiowaves in radio and television communication2. microwaves in satellite television and microwave oven3. infra-red waves in infra-red remote controllers and

intruder alarms4. light in optical fibres for medical uses and

telecommunications5. ultra-violet in sunbeds, and sterilisation6. X-rays in radiological and engineering applications7. Gamma rays in medical treatment

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

Electromagnetic Spectrum

Properties An electromagnetic wave is produced by the

simultaneous vibration of electric and magnetic fields.

All electromagnetic waves transfer energy from one place to

another are transverse waves can travel through vacuum. They DO NOT

require any medium to travel from one point to another.

travel through a vacuum at the speed of 3 x 108 ms-1.

obey wave properties like reflection and refraction.

carry no electrical charge as they are neither positively nor negatively charged.

obey the wave equation: v = f.

If electromagnetic waves travel in vacuum, then for the If electromagnetic waves travel in vacuum, then for the wave equationwave equation

v = v = ff v = v = cc, , where c is the symbol for the speed of light in vacuumwhere c is the symbol for the speed of light in vacuum

cc = = ff 3.0 x 103.0 x 1088 = = ff

Their frequencies do not change when they travel from Their frequencies do not change when they travel from one medium to another.one medium to another. (e.g.. From water to glass). This (e.g.. From water to glass). This is because their frequency ƒ depends only on the source is because their frequency ƒ depends only on the source of the wave. Only their speeds and wavelengths change of the wave. Only their speeds and wavelengths change from one medium to another.from one medium to another.

Components of electromagnetic spectrumComponents of electromagnetic spectrumComponents of electromagnetic spectrumComponents of electromagnetic spectrum

Speed in a vacuumis constant

c = 3 x 108 m s-1

Electromagnetic SpectrumElectromagnetic Spectrum

Gamma Gamma raysrays X-raysX-rays Ultraviolet Ultraviolet Visible Visible

lightlight InfraredInfrared MicrowaveMicrowave Radio Radio wavewave

low frequency

high frequency

short wavelength

long wavelength

Several km

< 10-12 m

Electromagnetic spectrumElectromagnetic spectrum

“Ronald McDonald Is Very Ugly eXcept Gary”

For each component, you need to knowFor each component, you need to know

• Range of wavelengthRange of wavelength

• Its usesIts uses

• Any harmful effects (The higher the frequency, Any harmful effects (The higher the frequency, the larger the amount of energy)the larger the amount of energy)

• SourceSource

• Detector Detector

For each component, you need to knowFor each component, you need to know

• Range of wavelengthRange of wavelength

• Its usesIts uses

• Any harmful effects (The higher the frequency, Any harmful effects (The higher the frequency, the larger the amount of energy)the larger the amount of energy)

• SourceSource

• Detector Detector

Applications of electromagnetic spectrumApplications of electromagnetic spectrumApplications of electromagnetic spectrumApplications of electromagnetic spectrum

Radio waveRadio wave has wavelength of 10has wavelength of 10-1-1 to 10 to 1055 m m

Can move around obstaclesCan move around obstacles

is used in radio communication and television transmission is used in radio communication and television transmission over long distances (LW, MW, SW, VHF, UHF). Radio over long distances (LW, MW, SW, VHF, UHF). Radio telescope.telescope.

Television transmission is made possible Television transmission is made possible with the use of VHF and UHF radio waveswith the use of VHF and UHF radio waves

source: TV and radio transmitterssource: TV and radio transmitters

detector: aerials of TV and radio detector: aerials of TV and radio receivers/antenna receivers/antenna

MicrowaveMicrowave

has wavelength of 10has wavelength of 10-3-3 to 10 to 10-1-1 m (0.001 m to 0.1m) m (0.001 m to 0.1m)

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

travels in straight line without losing much of its energytravels in straight line without losing much of its energy

source: electronic devices source: electronic devices (eg. cavity magnetron in (eg. cavity magnetron in microwaves)microwaves)

detector: microwave detector: microwave receiversreceivers speed-monitoring speed-monitoring

radarradarsatellite stationsatellite station

Infrared radiationInfrared radiation is the radiation beyond the red end of the visible

spectrum

has wavelength of 10-7 to 10-3 m

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

is emitted by hot objects

source: warm bodies

detector: special photographic films, blackened thermometers and thermocouples an infra-red photographan infra-red photograph

Visible light 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 analysis and photosynthesis, endoscopy. Lasers for medical, industrial and surveying use.

source: hot bodies, lasers and sun

detector: eyes, photographic film and photocells

laser surgerylaser surgery

Ultraviolet radiationUltraviolet radiation has wavelength of 10has wavelength of 10-8-8 to 10 to 10-7-7 m m

stimulates our bodies to produce vitamin Dstimulates our bodies to produce vitamin D

Can cause tanning, overexposure can lead to skin cancerCan cause tanning, overexposure can lead to skin cancer

is used in sunbeds, fluorescent tubes, is used in sunbeds, fluorescent tubes, sterilisation, forgery detection and sterilisation, forgery detection and fluorescence in washing powdersfluorescence in washing powders

source: sun, mercury vapour and source: sun, mercury vapour and lampslamps

detector: photographic film, detector: photographic film, fluorescent screens, dyes and fluorescent screens, dyes and photocellsphotocells

overexposure to UV radiation can overexposure to UV radiation can cause skin cancercause skin cancer

X ray has wavelength of 10has wavelength of 10-13-13 to 10 to 10-8-8 m m

is penetrating and can cause damage to tissues is penetrating and can cause damage to tissues and organismsand organisms

Doctors, nurses and people working in X-ray Doctors, nurses and people working in X-ray environment have to wear protective clothing environment have to wear protective clothing to shield themselves from X rayto shield themselves from X ray

is used in medical and dental diagnostic tools is used in medical and dental diagnostic tools and engineering applications. Check for and engineering applications. Check for flaws/cracks in metals. Detect artwork forgery. flaws/cracks in metals. Detect artwork forgery. Airport scanners. Crystal structure analysis.Airport scanners. Crystal structure analysis.

source: x-ray tubessource: x-ray tubes

detector: photographic film and fluorescent detector: photographic film and fluorescent screensscreens

x-ray photograph of handx-ray photograph of hand

Gamma ray (HIGHEST ENERGY!!!!, HIGHEST FREQUENCY) has wavelength of 10-14 to 10-10 m

is penetrating and can cause damage to living tissues and organisms

is used in treatment of cancer (gamma knives – sharp beam of gamma ray) and checking of welds, under controlled situations. Sterilising equipment.

source: cosmic rays, radioactive substances and nuclear reaction

detector: Geiger-Müller counters (GM tube), bubble/cloud chambers and photographic film

Effects of EM Waves on Cells and Tissue

Exposure to electromagnetic radiation primarily causes heating effects such as the pain of sunburn or skin cancer. However, over-exposure may result in harmful effects such as pain of sunburn or skin cancer.

EM waves can be classified as either ionising radiation or non-ionising radiation:

• Ionising radiations are extremely high frequency EM waves which include X-rays and gamma rays. They have enough photon energy to produce ionisation (a process where one or more electrons are removed from a neutral atom by radiation). It is a harmful process leading to destruction or modification of living cells.

• Non-ionising radiations are the part of the EM spectrum which has photon energies too weak to produce ionisation. Examples are ultra-violet, visible light, infra-red radiation, microwave and radio wave.

Memory aid (song) for Electromagnetic Spectrum

http://www.youtube.com/watch?v=bjOGNVH3D4Y

Electromagnetic Electromagnetic waveswaves

c = 3 x 10c = 3 x 108 8 m sm s-1-1

Transverse Transverse waveswaves

areare

with speed in with speed in vacuumvacuum

ComponentComponentss

Radio wavesRadio waves

Microwaves Microwaves

Infra-red Infra-red waves waves . .

Light Light

Ultra-violet Ultra-violet ..

X-raysX-rays

Gamma raysGamma rays

ApplicationsApplications

Radio and television Radio and television communicationcommunication

Satellite television and Satellite television and telephonetelephone

Home electrical appliances, Home electrical appliances, remote controls and intruder remote controls and intruder alarmsalarms

Optical fibres in medical usage Optical fibres in medical usage and telecommuncationand telecommuncation

Sunbeds, fluorescent tubes and Sunbeds, fluorescent tubes and sterilisationsterilisation

Medical use and engineering Medical use and engineering applicationsapplications

Medical treatmentMedical treatment

consist ofconsist of

Reference:http://blogs.edf.org/climate411/2007/07/25/greenhouse_effect/

http://www.ehow.com/how_2001650_advantages-dishnetwork-cable.html

http://www.smh.com.au/news/technology/police-grapple-with-defective-detectors/2008/07/22/1216492432489.html

http://www.teara.govt.nz/en/auckland-places/1/4

http://www.snowyrangevision.com/laserSurgery.html

http://www.faqs.org/photo-dict/phrase/710/x-ray.html