Waves

• Waves


  A way of transmitting information or energy
• Waves send information from one place to another
• In a wave, the matter at the start of the wave doesn't move along the wave, just the energy and information does
• When someone says something, the air particle doesn't shoot off from their mouth to hit you in the ear. It means the information and energy is passed from particle to particle of the wave
• How Waves Move


  1. Longitudinal

  2. Transverse
• Longitudinal wave


  • Vibration in the same plane (direction) as the way the wave is moving
  • Compression
  • Rarefaction
• Transverse wave


  • Vibration perpendicular to the direction the wave travels
• Wave characteristics


  • Amplitude
  • Wavelength
  • Frequency
• Amplitude


  The height of the wave from the MIDDLE to the TOP or BOTTOM. It is NOT from the top to bottom of the wave
• Wavelength


  The length of the wave from one crest to the next, or one trough to the next. It is measured in metres
• Frequency


  How many waves happen per second and it's measured in Hertz (Hz)
• A normal man speaks at a frequency of about 100Hz, which means the wave is repeating 100 times every second
• The higher the frequency, the higher pitched the sound
• Types of waves


  • Transverse
  • Longitudinal
• Transverse waves


  • All electromagnetic waves
  • Water waves
  • Secondary seismic waves
• Longitudinal waves


  • Sound waves
  • Infrasound
  • Ultra Sound
  • Primary seismic waves
• Transverse wave


  A wave where the motion of the particles is perpendicular to the direction of wave propagation
• Waves interact with objects that are in the way (boundaries) in many different ways. They can reflect, refract or diffract, and sometimes they do all three
• When drawing a wave or ray diagram to show these interactions, you must always follow rules: 1) Use a ruler, 2) Draw a normal line (perpendicular to the object), 3) Measure any angles to the normal using a protractor
• The angle at which the light hits a boundary is called the angle of incidence. The angle at which it reflects is called the angle of reflection
• When waves meet a place where the density of the material changes, the speed of the wave changes
• If the waves are meeting this change in density at an angle, this causes the wave to bend due to this change in speed. This is called refraction
• When a wave slows down, the previous wave catches up with the first wave. This means the distance between waves (the wavelength) gets shorter
• Nothing can travel faster than the speed of light (3x10^8 m/s)
• Wave speed equations


  1. Speed = Distance / Time

  2. Speed = Wavelength x Frequency
• The equation to use depends on what information is given in the question