EM

• Electromagnetic waves

  Consist of magnetic fields and vibrating electricity, which transmit energy across space or through matter
• Electromagnetic waves

  • Travel at the speed of light (around 300 million metres per second)
  • Are neither deflected by a magnetic field or an electric field, but are capable of showing diffraction or interference
  • Have a frequency ranging between thousands of waves per second, to trillions of waves per second
  • Have a wavelength ranging between the length of a soccer field, to being shorter than the diameter of an atom
• Electromagnetic waves can travel through all mediums, but can also propagate through the absence of a medium (that is, in a vacuum)
• All electromagnetic waves are also known as transverse waves, in which particles do not move, but rather oscillate up and down on their individual equilibrium positions
• Wavelength, frequency and speed of light

  Wavelength x frequency = speed of light
• Regions of the electromagnetic spectrum

  • Radio waves
  • Microwaves
  • Infrared
  • Visible light
  • Ultraviolet (UV)
  • X-rays
  • Gamma rays
• Radio waves

  Emitted and received by antennas, used for controlling remotes and industrial heating
• Microwaves


  Radio waves with short wavelengths, can penetrate materials below the surface and deposit their energy
• Infrared

  Divided into three parts: far-infrared, mid-infrared and near-infrared
• Visible light


  The part of the electromagnetic spectrum in which the human eye is most sensitive to
• Ultraviolet (UV)

  Exposure can cause damage to living tissues, known to cause sunburns due to UV radiation on skin cells, which can lead to skin cancer
• 1. x-rays


  Used as probes to see through objects with thicknesses
• Gamma rays

  Have the most energetic photons, with no defined lower limit when it comes to their wavelength, used for irradiation of seeds and foods for sterilisation and used in medicine for radiation cancer therapy
• Ionisation


  The process where an electron is given enough energy to break away from an atom, resulting in the formation of two charged ions or particles
• Ionising radiation can be produced from artificial or natural sources
• Ionising radiation


  1. rays, gamma rays and the higher ultraviolet part of the electromagnetic spectrum
• Non-ionising radiation

  Waves with lower frequency, longer wavelength and lower energy
• Non-ionising radiation does not penetrate deep into the tissues, but can cause damage to our skin and eyes
• Ionising radiation is known to cause damage to living tissues as they can cause chemical changes through the breaking of chemical bonds
• The sun's rays are a form of electromagnetic radiation

  Ultraviolet rays from the sun cause effects like suntan and sunburn, as the rays can penetrate the surface layers of our skin
• Radiation-caused cellular damage


  May lead to cancer
• Electromagnetic waves with higher energy, such as x-rays


  Can penetrate deeper into our bodies, passing through soft tissues but not through hard tissues such as bone
• If we are exposed to x-rays for an extended period, they could cause DNA damage
• Heating

  Involves heat transfer and absorption of electromagnetic waves, whereby any material exposed to the electromagnetic radiation will heat up
• Applications of electromagnetic waves

  • Radio waves for communication uses, such as television communication and radio
  • Microwaves used in a microwave oven to heat meals, and for satellite television
  • Infrared used in security cameras to detect intruders, or for night vision
  • Visible light used in optical fibres for telecommunications and medical imaging technology
  • Ultraviolet photochromic ink used to counter forgery of banknotes, as banknotes with this security feature glow fluorescent under UV light
  • X-rays used in X-ray machines to detect the bone structure, useful for detecting injuries, monitoring recovery, and so on
  • Gamma rays used in cancer radiation therapy to kill off cancer cells
• the speed of light =299792458m/s