Waves

• Longitudinal waves:

  Waves where vibrations are parallel to the direction of wave travel.

  eg:

  • Sound Waves
  • Ultrasound Waves
  • Seismic P-Waves
• Longitudinal wave diagram:

  A) Longitudinal

  B) sound

  C) wavelength

  D) compression

  E) rarefaction

  F) movement

  
• Parts of a longitudinal wave:

  Compression -> Regions of high pressure (particles close). They 'store' the energy of the wave, moving in the direction of travel.

  Rarefaction -> Regions of low pressure (particles far apart).
• Transverse waves:

  Waves where vibrations are at right angles to the direction of travel.

  eg:

  • EM Waves
  • Seismic S-Waves
• Transverse waves diagram:

  A) Transverse

  B) Wavelength

  C) Crest

  D) Trough

  E) Cycle

  F) Amplitude

  G) Direction of travel

  
• Parts of a transverse wave:

  Peak -> The highest point in a wave. Energy is stored here.

  Trough -> The lowest point in a wave. Energy is stored here.
• AMPLITUDE:

  The maximum displacement of a point of a wave from its rest position.
• WAVEFRONT:

  An imaginary surface representing corresponding points in separate waves, which vibrate in unison.
• FREQUENCY:

  The number of oscillations (waves) passing a point in a second.
• WAVELENGTH:

  Distance covered by a full cycle of the wave.
• TIME PERIOD:

  Time taken for a full cycle of the wave.
• Waves transfer energy and information WITHOUT transferring matter.
• Wavespeed = Frequency * Wavelength

  Frequency = Speed / Wavelength

  Wavelength = Speed / Frequency

  A) Speed

  B) V

  C) Frequency

  D) f

  E) Wavelength

  F) lamda

  
• 1 = Frequency * Time Period

  Frequency = 1 / Time Period

  Time Period = 1 / Frequency

  A) 1

  B) f

  C) T

  
• The Doppler Effect:

  The change in the observed frequency of a wave when its source is moving towards or away from the observer.

  • As the source approaches the observer, the frequency increases (higher pitch).
  • As the source moves away from the observer, the frequency decreases (lower pitch).

  It is caused by the compression or expansion of the waves due to the relative motion of the source and observer.
• The Doppler effect diagram:

  A) Low

  B) High

  
• The EM spectrum:

  Light is part of a continuous EM spectrum, in which all waves travel at the same speed in a vacuum.
• • Radio (Rabbits)
  • Microwave (Meet)
  • Infrared (In)
  • Visible (Very)
  • Ultraviolet (Unusual)
  • X-Ray (X-pensive)
  • Gamma Ray (Gardens)
• • - Wavelength = + Frequency = + Energy
  • + Wavelength = - Frequency = - Energy
• • Wavelength increases towards radio waves.
  • Frequency and energy increases towards gamma rays.
• Uses of the waves:

  • R -> Broadcasting and communications
  • M -> Cooking and satellite communications
  • I -> Heaters and night vision
  • V -> Optical fibres and photos
  • U -> Fluorescent lamps
  • X -> Medical and seeing internally
  • G -> Sterilising food and medical equipment
• Dangers of the waves:

  • R -> None
  • M -> Internal heating of body tissues
  • I -> External skin burns
  • V -> None
  • U -> Damage to surface cells and blindness
  • X -> None
  • G -> Cancerous radiations and mutations
• To prevent risks from EM radiation, limit exposure to radiation and cover your body when using.
• The frequency range for human hearing is 20 - 20,000 Hz.