P1b: em waves SJT

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AQA GCSE Physics Year 10 Unit 1b: em waves- revision

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P1b: em waves SJT

  1. 1. Radiation and the Universea.Electromagnetic Waves Mr S Thompson
  2. 2. Electromagnetic Radiation Electromagnetic (em) radiation is basically a movement of energy in the form of a wave. Some examples:
  3. 3. The Electromagnetic Spectrum High frequency, short wavelength Low frequency, long wavelength γ Each type of radiation shown in the electromagnetic spectrum has a different wavelength and a different frequency: Each of these types travels at the same speed (300,000,000m/s), and different wavelengths are absorbed by different surfaces.
  4. 4. The Electromagnetic Spectrum Type of radiation Uses Dangers Treating cancer, sterilisation Gamma rays Cell mutation X rays Medical Cell mutation Ultra violet Sun beds Skin cancer None (unless you look at the sun) Visible light Seeing things Remote controls, heat transfer Infra red Sunburn Microwaves Satellites, phones Very few TV/radio Communications Very few
  5. 5. Transmitting information Optical fibres have two main advantages: they can send more information compared to electrical cables of the same diameter and with less signal weakening. Microwaves are used in mobile phone networks.
  6. 6. The Wave Equation V  f All E-M waves obey the Wave Equation: Wave speed (v) = frequency (f) x wavelength () in m/s in Hz in m
  7. 7. Analogue vs. Digital Signals + 1 - 0 Analogue signals (like talking or music) continually vary in amplitude and/or frequency Digital signals, however, are either off or on, and the information is sent in a series of pulses There are two main advantages of digital: More information can be sent down the same cable Better quality, because a digital signal can be amplified without amplifying the extra noise:

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