Electromagnetic Spectrum

• Electromagnetic waves

  • Transverse Waves
• Transfer of energy in Electromagnetic waves

  • from the source to the absorber
• Source to absorber example

  • microwave source to food
  • sun emits energy to earth
• Speed of electromagnetic waves

  • same speed through a vacuum (space) or air
• Vacuum

  • means electromagnetic waves do not need particles to move
  • non-mechanical waves
• Speed of ALL electromagnetic waves

  • 3.3 x 10^8
• The beginning of the electromagnetic spectrum

  • radio waves
  • microwaves
  • infrared
• Wavelength + frequency of starting electromagnetic waves

  • low frequency
  • thus, longer wavelength
  • low energy
• Ending electromagnetic waves

  • shorter wavelength
  • thus, higher frequency
  • high energy
• Trend in Electromagnetic Spectrum

  • low to high frequency
  • long to short wavelength
  • low to high energy
• All types of Electromagnetic Waves Beginning to End

  1. radio waves
  2. microwaves
  3. infrared waves
  4. visible light
  5. ultraviolet (UV)
  6. X-rays
  7. Gamma rays

  
• Eyes and Visible Light

  • Eyes can only detect visible light
  • Frequency range that is detectable to the human eye
• Visible Light

  • red
  • orange
  • yellow
  • green
  • blue
  • indigo
  • violet
• Transparent objects

  • Transmit light
• Translucent objects

  • partial transmission of light
  • light rays are scattered
• Visible light

  • passes through a prism
  • will disperse into spectrum of colours
• Each colour in Visible light

  • own frequency
  • own wavelength
• Red

  • longest wavelength
  • refracts the least
  • fastest
• Violet

  • shortest wavelength
  • refracts the most
• Wavelength speed of Visible Light

  • Shorter wavelengths slow down more than longer wavelengths
• Why does dispersion of white light occur when entering into a prism?

  • The different wavelengths refract a different amount
  • therefore, spread out creating a rainbow effect
• Radio waves

  • Produced by oscillations in electrical circuits
• What happens when radio waves are absorbed?

  • create an alternating current
  • has the same frequency of the radio waves
• Gamma rays

  • Originate from changes in the nucleus of an atom
• Gamma rays : When electrons move to a higher energy level.. 


  • gets further from the nucleus
  • the atom has absorbed EM radiation
• Gamma rays : When electrons have moved to a lower energy level

  • closer to the nucleus
  • atom emits EM radiation
• Gamma rays : What happens when electrons gain enough energy?

  • It can leave the atom to form an ion
  • Therefore, gamma rays occur from changes in the nucleus of an atom
• Effects of UV light, X-rays and Gamma

  • Hazardous effects on human body tissue
  • Depend on the type of radiation + size of radiation dose
• Radiation dose

  • how much exposure leads to harm on a person
• Negative effects of UV light

  • skin aging prematurely
  • increase risk of skin cancer
• Negative effects of X-rays and Gamma radiation

  • ionising radiation
  • cause mutation of genes
  • leads to cancer
• Precautions with X-Ray and Gamma radiation

  To ensure minimal exposure :

  • stand a reasonable distance away
  • use protective shielding e.g lead
• Uses of radio waves

  • Television
  • Radio
• Why can radio waves be used in TV and Radio?

  • long wavelength
  • can travel far without losing quality
• Uses of Microwaves

  • Satellite communications
  • Cooking food
• Why are microwaves of good use for satellite communications?

  • can penetrate atmosphere
  • to reach satellites
• Infrared

  • Electrical heaters
  • Thermal imaging cameras
• Why are Infrared radiation of good use for cooking food?

  • transfers thermal energy
• Uses of Visible Light

  • Fibre optic communications
  • Photography
• Why is Visible light of good use for fibre optic communications?

  • Best reflection / scattering in glass
  • Optimal wavelength