Waves and EM Spectrum

• Electromagnetic waves


  Transverse waves
• Electromagnetic waves transfer energy (not matter)
• Electromagnetic spectrum


  A continuous spectrum
• Order of the electromagnetic spectrum in order of increasing wavelength

  • Gamma
  • X Ray
  • UV
  • Visible
  • Infrared
  • Microwaves
  • Radio
• Highest frequency electromagnetic wave

  Gamma waves
• Highest energy electromagnetic wave

  Gamma waves
• Properties shared by all electromagnetic waves

  • They are all transverse waves
  • They all travel at the same speed (3x10⁸ m/s)
  • They can travel through a vacuum
• Range of frequencies of electromagnetic waves detected by the human eye

  400-700 nanometres
• Electromagnetic waves all travel at the same speed in a vacuum and in air
• What can happen when radiation strikes an object

  • Transmitted
  • Reflected
  • Absorbed
• Oscillations in an electrical circuit

  Can produce radio waves
• How radio waves create an alternating current in a circuit

  Radio waves are absorbed, they can induce oscillations in a circuit with the same frequency as the waves themselves
• Gamma rays


  Originate from changes in the nuclei of atoms
• Ultraviolet waves


  • Can cause the skin to age prematurely
  • Can increase the risk of developing skin cancer
• 1. rays and Gamma rays

  • They are ionising radiation so can cause mutations in genes
  • They can lead to increased risk of developing various cancers
• Infrared rays


  • Can cause burns to skin/tissue
• How electromagnetic radiation affects electron arrangement in atoms

  Absorption or emission of electromagnetic radiation can cause electron arrangement to change (It can remove electrons from the atom or move electrons further from the nucleus)
• Atoms become ions


  By losing an outer electron
• Effects of body cells absorbing radiation

  • Large amounts can damage cells
  • Smaller amounts cause mutation, causing cells to divide rapidly, which can lead to cancer
• Use of radio waves


  Communications, because radio waves are long wavelength and can travel long distances without losing quality
• Use of microwaves


  Cooking, as microwaves are absorbed by and heat fat/water in foods
• Uses of infrared radiation

  • Cooking food (as it transfers thermal energy)
  • Infrared cameras
  • Short range communication
• Uses of visible radiation


  Illuminating (i.e. seeing) and fibre optics, as they reflect best in glass (other waves have wavelengths that are too long/short)
• Uses of UV radiation

  • Sterilisation, as it kills bacteria
  • Energy efficient lamps, as it radiates low heat but high energy
  • Sun tanning etc.
• Uses of X rays

  Medical imaging and treatment, because they are very high energy and can easily penetrate body tissues
• Uses of gamma rays


  Gamma rays are used in medical treatments, such as radiotherapy in the treatment of cancer
• Most dangerous waves of the EM spectrum

  • Gamma and X rays, as they have the highest energy
• Wave speed = frequency x wavelength
• Frequency (f) is measured in Hertz (Hz). One hertz means one cycle per second.
• The wavelength is the distance between two consecutive peaks or troughs.
• Oscillations in an electrical circuit

  Can produce radio waves
• How radio waves create an alternating current in a circuit

  Radio waves are absorbed, they can induce oscillations in a circuit with the same frequency as the waves themselves
• Gamma rays


  Originate from changes in the nuclei of atoms
• Ultraviolet waves


  • Can cause the skin to age prematurely
  • Can increase the risk of developing skin cancer
• 1. rays and Gamma rays

  • They are ionising radiation so can cause mutations in genes
  • They can lead to increased risk of developing various cancers
• Infrared rays


  • Can cause burns to skin/tissue
• How electromagnetic radiation affects electron arrangement in atoms

  Absorption or emission of electromagnetic radiation can cause electron arrangement to change (It can remove electrons from the atom or move electrons further from the nucleus)
• What do all bodies (objects) emit and absorb?

  Infrared radiation
• As temperature increases


  The quantity of infrared radiation emitted by an object increases
• As temperature increases


  The type of radiation emitted by an object becomes shorter wavelength (e.g. X-rays and gamma rays)