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Electromagnetic Spectrum

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A set of slides created to teach Electromagnetics Spectrum to learners at Bishops Diocesan College in Cape Town.

A set of slides created to teach Electromagnetics Spectrum to learners at Bishops Diocesan College in Cape Town.


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  • 1. Electromagnetic Spectrum Keith Warne
  • 2. Electromagnetic Waves Current Right Hand Dynamo Rule Field  Transmitter (Signal generated alternating current)  Thrust/movement Receiver: EM waves can be generated and detected by changing (accelerating) electric currents in a conductor (arial) SAMPLE ONLY (Signal Received – weak alternating current induced – needs amplification) SAMPLE ONLY of Direction  SAMPLE ONLY movement For FULL presentation click HERE >> www.warnescience.net
  • 3. Electromagnetic Spectrum INCREASING FREQUENCY and ENERGY INCREASING W A V   E L E N G T H All the different types of electromagnetic waves form the Electromagnetic Spectrum. Changing the frequency changes the properties of the waves. SAMPLE ONLY SAMPLE ONLY SAMPLE ONLY For FULL presentation click HERE >> www.warnescience.net
  • 4. Microwaves    Microwaves have wavelengths that can be measured in centimeters! The longer microwaves, those closer to a foot (~30 cm) in length, are the waves which heat our food in a microwave oven. Microwaves are good for transmitting because microwave energy can penetrate haze, light rain and snow, clouds, and smoke. SAMPLE ONLY SAMPLE ONLY SAMPLE ONLY For FULL presentation click HERE >> www.warnescience.net
  • 5. Visible Light    Visible light is made up of the various frequencies of colored light. The colour is determined by the frequency of the light. When electromagnetic radiation of this frequency falls on our retina our brain interprets it as colour. Longer wavelengths are refracted the SAMPLE ONLY SAMPLE ONLY LEAST! SAMPLE ONLY For FULL presentation click HERE >> www.warnescience.net
  • 6. Energy of a Light • Energy of a photon E = hf Max Planck • Wave equation  = f x  • speed of light = c To calculate the energy of a photon of light with wavelength  and speed c .: E = h(c/ ) h = 6.63 X 10-34 J.s Eg, Calculate the energy of a photon of blue light. E = hf = (6.63x10-34)*(3x108/450x10-9) = 4.4x10-9J SAMPLE ONLY SAMPLE ONLY SAMPLE ONLY For FULL presentation click HERE >> ScienceCafe
  • 7. Polarization The electric and magnetic fields in light oscillate in ALL DIRECTIONS. A Polaroid filter allows the ELECTRIC field through in ONE PLANE only – i.e. the light has been PLANE POLARISED. If a second Polaroid filter is placed at 90o to the first NO LIGHT WILL PASS THROUGH! SAMPLE ONLY SAMPLE ONLY SAMPLE ONLY For FULL presentation click HERE >> ScienceCafe
  • 8. EM Summary Radiation Produced () Penetration USE Radioactive decay () Rel. Size Cathode ray tubes  X High energy electron collisions UV Visible Sun / lamps IR heat Micro Magneto White Hot objects Radio SAMPLE ONLYAlternating current SAMPLE ONLY SAMPLE ONLY
  • 9. WarneScience Hi… This is a SAMPLE presentation only. My FULL presentations, which contain a lot more slides and other resources, are freely available on my resource sharing website: www.warnescience.net (paste into your browser if link above does not work) Have a look and enjoy! Keith Warne