Waves

• Define 'transverse wave'

  The vibrations/oscillations of the waves are perpendicular to the direction of energy transfer
• Define 'longitudinal waves'

  the vibrations/oscillations of the waves are parallel to the direction of energy transfer
• Define 'amplitude'

  The maximum displacement of a point on a wave away from its rest position
• Define 'wavelength'

  The length of a complete wave cycle
• The equation linking time period and frequency

  Time period = 1 / frequency
• What are the units for frequency?

  Hz/Hertz
• The equation linking wave speed, frequency and wavelength

  wave speed = frequency x wavelength
• Are electromagnetic waves transverse or longitudinal?

  Transverse
• What do EM waves transfer?

  Energy
• Why are EM waves not mechanical waves?

  They can travel through a vacuum
• What is the order of the electromagnetic waves from lowest to highlest frequency?

  • radio waves
  • microwaves
  • infrared
  • visible light
  • ultraviolet
  • x-rays
  • gamma
• How do light waves travel?

  In straight lines
• Which waves travel faster: light or sound?

  Light waves
• What is an echo?

  A reflection of a wave when it hits a boundary
• Describe reflection off a plane surface

  The angle of incidence is equal to the angle of reflection
• What is a luminous object?

  An object that emits light
• What is superposition?

  When two waves interact with each other. They can either cancel each other out or make each other more intense.
• What can occur when an EM wave meets a substance?

  It can be absorbed, transmitted refracted or reflected
• Define 'medium' (media is plural)

  A substance e.g, water, air, glass
• Why does refraction happen?

  When a wave moves from one medium to another, with a different optical density, it causes a change in velocity
• How can EM waves be produced?

  When electrons become de-excited, they emit EM radiation
• How can radio waves be produced?

  By creating oscillations in an electrical circuit
• How can we detect radio waves?

  They generate an alternating current with the same frequency
• What is radiation dose?

  A measure of the risk of harm resulting from an exposure of the body to the radiation
• Which EM waves are ionising?

  Ultraviolet, x-rays, gamma
• What are the dangers of ultraviolet waves?

  Can cause skin to age prematurely and increase the risk of skin cancer
• What are the dangers of x-rays and gamma rays?

  Can cause the mutation of genes which can lead to cancer
• What can radio waves be used for?

  Television and radio
• What can microwaves be used for?

  Satellite communications and cooking food
• What can infrared be used for?

  Electrical heaters, cooking food and infrared cameras
• What can visible light be used for?

  Fibre optic communications, photography and traffic lights
• What can ultraviolet be used for?

  Energy efficient lamps, sun tanning and checking bank notes
• What can x-rays be used for?

  Medical imaging and airport security
• What can gamma rays be used for?

  Sterilising equipment and medical treatment
• Why are x-rays used for medical imaging?

  They pass through flesh but not bone
• Why are gamma rays used for treating cancer and sterilising medical equipment?

  High doses kill cells and bacteria
• Which surfaces absorb radiation?

  All surfaces, black matt is the best absorber, white shiny is the worst
• Which surfaces emit radiation?

  All surfaces, black matt is the best emitter, white shiny is the worst
• Which surfaces are the best reflectors?

  Shiny