Radio waves Em waves and uses

• Radio Waves are Made by Oscillating Charges
• How radio waves are made

  1. Oscillating charges

  2. Produce oscillating electric and magnetic fields

  3. Electromagnetic waves are produced
• You can produce radio waves using an alternating current in an electrical circuit
• The frequency of the waves produced will be equal to the frequency of the alternating current
• Transmitter


  The object in which the charges (electrons) oscillate to create the radio waves
• How radio waves are received

  1. Radio waves reach the receiver

  2. Absorbed by the material of the receiver

  3. Cause electrons in the receiver to oscillate

  4. Generate an alternating current with the same frequency as the radio wave
• Radio Waves are Used Mainly for Communication
• Radio waves


  • Wavelengths longer than about 10 cm
  • Can be transmitted long distances and bend around the curved Earth
  • Short-wave signals can be received at long distances by reflecting off the ionosphere
  • FM and TV signals require line of sight with the transmitter
• Uses of radio waves


  • Communication to and from satellites
  • Microwave ovens
  • Detecting infrared radiation with infrared cameras
• Fibre Optic Cables Use Visible Light to Transmit Data
• Optical fibres


  • Thin glass or plastic fibres that can carry data as pulses of visible light
  • Light is reflected back and forth inside the fibre
  • Light is not easily absorbed or scattered as it travels
• Ultraviolet Radiation Gives You a Suntan
• 1. rays and Gamma Rays are Used in Medicine
• Uses of X-rays and gamma rays in medicine

  • X-ray imaging to see broken bones
  • Radiotherapy to treat cancer
  • Medical tracers using gamma radiation
• Some EM Radiation Can be Harmful to People
• Harmful effects of EM radiation

  • Low frequency waves like radio waves are mostly harmless
  • High frequency waves like UV, X-rays and gamma rays can cause damage to cells and tissues
• Radiation dose


  Measure of the risk of harm from exposure to radiation, measured in sieverts
• Risk from radiation can be different for different parts of the body
• Radiation doses for CT scans

  • Head: 2.0 mSv
  • Chest: 8.0 mSv