1.5 - Features of Waves

• Reflection

  • Waves can reflect from boundaries

  • Water waves reflect from barriers

  • Light waves reflect from mirrors
• Refraction

  • Waves can change direction when they travel into a different material

  • This is because they change speed due to the density of the material
• Refracted Water Waves

  • Water waves can also be refracted when they travel between deep and shallow water

  • Water travels slower in shallow water
• Satellite communication

  There are two kinds of satellite used, both take 24 hours to orbit.

  • Geosynchronous returns to the same point once every 24 hours.
  • Geostationary stays above the same point at all times.
• A transverse wave has vibrations perpendicular to the direction of travel.
• Transverse waves = Wavy
• Waves transfer energy from one place to another without transferring any matter
• Particles vibrate as the waves travel and transfer the energy between them
• energy is transferred in the direction the waves are travelling
• The crest is the top of one wave
• The trough is the bottom of one wave
• The frequency of a wave is the number of waves per second
• Law of Reflection

  The angle of incidence is equal to the angle of reflection

  feta i = feta r
• The Electromagnetic Spectrum

  RADIOWAVES

  MICROWAVES

  INFRA RED

  VISIBLE

  ULTRA VIOLET

  X RAYS

  GAMMA
• Similarities in the ES- They all:

  • Travel the same speed in a vacuum
  • Reflect and Refract
  • Heats up any material that absorbs them
  • Transfer energy from one place to another
• All waves in the electromagnetic spectrum travel the same speed in a vacuum
• Radio waves have the longest wavelength
• Gamma waves have the highest energy and frequency
• All waves in the electromagnetic spectrum heat up any material that absorbs them
• All waves in the Electromagnetic spectrum transfer energy from one place to another
• Radio waves are used for:

  • communication
  • wifi
  • bluetooth
  • remote control cars
  • radio
  • television
• Microwaves are used for:

  • cooking food
  • mobile phones
  • speed cameras
  • satellite communication
• Dangers of Microwaves:

  Can cause internal heating of body tissue
• Uses of infrared:

  • cooking
  • heating
  • remote controls
  • night vision
  • security cameras
  • optical fibres
  • thermal imaging
• Dangers of infrared - burns to skin
• Visible Light Uses:

  • Seeing things
  • optical fibre broadband
• Dangers of Visible Light:

  • Can damage eyes
• Ultraviolet Uses

  • Sunbeds
  • Phototherapy
  • Detecting forgery
• Dangers of UV:

  • IONISING – Damages cells Causes cancer
• Uses of X-Rays:

  • Viewing bones
  • Airport Security
• Dangers of X-Rays: Can cause cancer if exposed for long periods of time Can cause damage to the eye
• Uses of Gamma Rays

  • Radiotherapy
  • Sterilising surgical equipment
• Dangers of Gamma Rays:

  • IONISING – Damages cells Causes cancer
• Microwaves are used for satellite communication
• Infrared and visible light are used for optical fibres
• Geosynchronous

  • takes 24 hours to complete one orbit
  • will only happen once every 24 hours
• Geostationary

  • a type of geosynchronous orbit
  • orbits the earth above a fixed position
  • takes 24 hours to complete one orbit
• Signals do not travel from satellite to satellite - they have to return to Earth each time
• advantages of optical fibres

  • cheaper
  • harder to bug
  • carry more information
  • experience less interference
  • easier/cheaper to access for repairs
• advantages of satellites

  • global coverage
  • anyone can access the signal