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ELECTROMAGNETIC SPECTRUMElectromagnetic Spectrum11Electromagnetic WavesElectromagnetic waves are emitted whenever charged particles oscillate or lose energy in some way. For example, the vibrating atoms in a hot, glowing bulb filament emit infrared and light, oscillating electric current emits radio waves. The higher the frequency of oscillation, or the greater the energy changes, the shorter the wavelength of the electromagnetic waves produced.

Electromagnetic Spectrum22Properties of Electromagnetic WaveRadio waves, microwaves, infra-red radiation, visible light, ultra-violet radiation, X-rays and gamma rays are all member of electromagnetic waves.Each type of radiation is produced and detected in its own special way.The wavelengths of electromagnetic waves range from extremely short for gamma rays to very long for radio waves.Electromagnetic Spectrum33

Electromagnetic Spectrum44All electromagnetic waves are transverse wavesElectromagnetic waves are produced by the simultaneous vibration of electric and magnetic field.

Electromagnetic Spectrum5

5Common features of all the electromagnetic waves include;They can travel through a vacuum.They travel through vacuum with the speed of light.They all show wave properties like reflection and refraction.They obey the wave equation v = f .The shorter the wavelength, the higher the frequency.As the frequency gets higher, the energy increases. Electromagnetic Spectrum66Radio WavesRadio waves have the longest wavelengths in the electromagnetic spectrum.They are used in radio and television communication to transmit sound and pictures.Radio waves are produced by oscillating electric currents in a transmitting aerial (or antenna).They are picked up by another aerial at the receiving end.Electromagnetic Spectrum77Family of Radio WavesLW (long wave), MW (medium wave), SW (short wave) are used for AM radio communication.VHF (very high frequency) is used for high quality FM stereo radio & terrestrial television communication.UHF (ultra high frequency) is used for terrestrial television communication.Electromagnetic Spectrum8

8MicrowavesMicrowaves are radio waves of very short wavelength.They have a wavelengths of a few centimetres.Microwaves are produced by special electronic devices such as the klystron tube.Electromagnetic Spectrum9

9Satellite Communication & TV

Microwaves are used for satellite communication and televisionElectromagnetic Spectrum10

10Radar SystemsRadar systems also used microwaves to find the direction and distance of objects.

Electromagnetic Spectrum11

11Microwave OvenMicrowaves is used for cooking as its wavelength are very strongly absorb by water moleculeElectromagnetic Spectrum12

12Rain disrupts Satellite TV?

Electromagnetic Spectrum13

Infra-red RadiationAll objects emit infra-red radiation.As an object gets hotter, the infra-red wavelength emitted gets shorter.At relatively low temperatures, all radiation is infra-red and cannot be seen by human eye.Electromagnetic Spectrum1414Thermogram Infra-red radiation emitted from a patients body enables doctors to diagnose cancerous growths and blocked blood circulationElectromagnetic Spectrum15

15Remote ControlThe remote unit communicates with the appliance via infra-red radiation which is produced by light emitting diodes (LED)Electromagnetic Spectrum16

16Intruder AlarmsThe alarm system is known as passive infra-red (PIR) motion detectorsElectromagnetic Spectrum17

17Visible LightVisible light is defined as part of electromagnetic spectrum that the human eye can be detect.The various wavelengths of light are classified by colours, ranging from violet with a wavelength of about 4 10-7 m to red with a wavelength of about 7 10-7 m.Electromagnetic Spectrum18

18Dispersion of LightAnother example of refraction is the dispersion of white light into its individual colors by a glass prism.As visible light exits the prism, it is refracted and separated into a magnificent display of colors.Each color from the original beam of light has its own particular wavelength (or color) and each wavelength is slowed differently by the glass. The amount of refraction increases as the wavelength of light decreases. Electromagnetic Spectrum1919Shorter wavelengths of light (violet and blue) are slowed more and consequently experience more bending than do the longer wavelengths (orange and red).Electromagnetic Spectrum20

20LaserLight in the form of laser light has a wide variety of applications in medicine, engineering and telecommunication.LASER is an acronym, which stands for Light Amplification by Stimulate Emission of Radiation.Electromagnetic Spectrum2121IndustriesLaser cutting through hard materials like steel and hundreds of layers of cloth to the same pattern simultaneouslyElectromagnetic Spectrum22

22MedicineLaser is used to spot weld a detached retina and for cauterising or sealing blood vessels.Electromagnetic Spectrum23

23Land SurveyingMeasuring a straight piece of road over large distanceElectromagnetic Spectrum24

24TelecommunicationDigital signals are sent by short pulses of laser light using optical fibresElectromagnetic Spectrum25

25Ultra-Violet RadiationUltra-violet radiation is the radiation beyond the violet end of the visible spectrum (wavelength range from 10-8 m to 10-7 m.The main source of ultra-violet radiation is sunlight.Electromagnetic Spectrum2626SunbedUV radiation from the Sun stimulates our body to produce vitamin D needed for healthy bone.Over-exposure to UV radiation can cause skin cancer and damage the retina.Electromagnetic Spectrum27

27SterilisingUV radiation kills bacteria and viruses.Low intensity UV lamps can reduce spoilage of meat.Electromagnetic Spectrum28

28Security MeasureSome chemicals flouresce when ultra-violet radiation falls on them where they absorb it and emit visible light which makes them glowElectromagnetic Spectrum29

29X-RaysX-rays are electromagnetic waves with wavelengths ranging from about 10-8 m down to 10-13 m.X-rays are produced when high energy electrons lose energy after striking a metal target.Electromagnetic Spectrum3030Diagnostic ToolExamine condition of persons bone & roots of teeth.Also used as treatment for certain forms of cancer.Electromagnetic Spectrum31

31NDTExamine the hidden flaws and cracks of metal partsInspecting inside electrical appliances to make sure that they have been assembled properlyElectromagnetic Spectrum32

32Gamma RaysGamma rays are electromagnetic waves emitted by radioactive nuclei.They are also released during nuclear reactions.Wavelengths of gamma rays range from 10-10 m to less than 10-14 m.Like X-ray, they are used to controlled situations to kill cancerous cells and checking flaws in metal.It is also used to sterilise hospital equipment.X-rays and Gamma rays are named differently according to how they are produced although their wavelengths overlap.Electromagnetic Spectrum3333RadiationWavelength / mUsesRadio wave10-1 - 105Radio and television communicationRadio telescopeMicrowave 10-3 10-1Satellite communication for satellite television and mobile phone networksMicrowave cookingRadar communicationInfra-red rays10-7 10-3Remote control of electrical appliancesIntruder alarmInfra-red photographyRadiant heaterVisible light10-7Optical fibres for medical uses and telecommunicationsPhotosynthesisLasers for medical, industrial and surveying uses.Electromagnetic Spectrum3434Electromagnetic Spectrum35RadiationWavelength / mUsesUltra-violet rays10-8 10-7Sun bedsSterilisationForgery detectionFluorescence effectX-rays 10-13 10-8Medical /dental inspectionsChecking weldsAnalysis of crystal structuresAirport securityTreatment of cancerGamma rays10-14 10-10Treatment of cancerChecking weldsSterilising equipment35Which statement is true for all electromagnetic waves?They are longitudinal.They can be seen.They have the same frequency in air.They travel at the same speed in a vacuum.Electromagnetic Spectrum3636Which wave is part of the electromagnetic spectrum?Electromagnetic Spectrum37

D37Radio waves, visible light and X-rays are all part of the electromagnetic spectrum.What is the correct order of increasing wavelength?Electromagnetic Spectrum38

D38The diagram represents some of the main parts of the electromagnetic spectrum.

What are the numbered parts?Electromagnetic Spectrum39

B39Which diagram shows the correct order of the waves in the electromagnetic spectrum?Electromagnetic Spectrum40

C40Which type of wave is used to send telephone signals to and from a satellite?infra-red waveslight wavesmicrowavessound wavesElectromagnetic Spectrum41Which type of radiation lies between visible light and microwaves in the electromagnetic spectrum?infra-redradio wavesultra-violetX-raysElectromagnetic Spectrum4242One of the effects of passing a ray of white light through a prism is to split the light into colours.

What is the name given to this effect?DeviationDispersionReflectionrefractionElectromagnetic Spectrum43

43When white light is dispersed by a prism, compared with blue light, the red light isslowed down less and refracted less.slowed down less and refracted more.slowed down more and refracted less.slowed down more and refracted more.Electromagnetic Spectrum44A student shines a narrow beam of white light into a prism as shown in the diagram. He sees a spectrum of colours emerging from the prism.Electromagnetic Spectrum45

Which three colours does he see at X, at Y and at Z?Electromagnetic Spectrum46

CThe diagram shows the spectrum produced when white light is dispersed by a glass prism.Electromagnetic Spectrum47

47What are the numbered visible colours?Electromagnetic Spectrum48

C48Light rays are deviated by a prism.Electromagnet