topic 7-Electromagnetism + magnetism

• Differences between types of electromagnetic (EM) waves

  • They make them useful to us in different ways
• There's a continuous spectrum of EM waves
• EM waves


  Waves that transfer energy
• EM waves


  • They travel at the same speed (the speed of light)
  • They can be classified into different types based on their frequency and wavelength
• Types of EM waves

  • Radio
  • Microwave
  • Infrared
  • Visible light
  • Ultraviolet
  • X-ray
  • Gamma ray
• EM waves are generated by a variety of changes in atoms and their nuclei
• Different EM waves are used for different purposes due to their different properties
• Refraction


  Waves changing direction at a boundary
• Refraction


  • When a wave crosses a boundary between materials at an angle, it changes direction
  • How much it's refracted depends on how much the wave speeds up or slows down, which usually depends on the density of the two materials
  • If a wave crosses into a material and slows down, it will bend towards the normal. If it speeds up, it will bend away from the normal
  • The wavelength of a wave changes when it is refracted, but the frequency stays the same
  • If the wave is traveling along the normal, it will change speed but not be refracted
• The optical density of a material is a measure of how quickly light can travel through it
• Constructing a ray diagram for refracted light

  1. Draw the boundary between the two materials and the normal

  2. Draw the incident ray and the angle of incidence

  3. Draw the refracted ray on the other side of the boundary
• Smooth surfaces like mirrors give clear reflections, while rough surfaces like paper cause diffuse reflection
• The angle of incidence always equals the angle of reflection