P6

• Waves


  One way in which energy may be transferred between stores
• Waves


  • Both mechanical and electromagnetic waves will transfer energy but not matter
• Oscillations


  Repeated and regular fluctuations, above and below the same position
• Vibrations


  Repeated movements back and forth (about a fixed point)
• Longitudinal waves


  Waves where the vibrations are parallel to the direction of wave travel
• Transverse waves


  Waves where the vibrations are at right angles to the direction of wave travel
• Mechanical waves


  • Cause oscillations of particles in a solid, liquid or gas and must have a medium to travel through
• Electromagnetic waves


  • Cause oscillations in electrical and magnetic fields
• All waves transfer energy but they do not transfer matter
• Parts of a wave


  • Rest position
  • Displacement
  • Peak
  • Trough
  • Amplitude
  • Wavelength
  • Time period
  • Frequency
• Waves are one way in which energy may be transferred between stores. Both mechanical and electromagnetic waves will transfer energy but not matter.
• Wave period


  The time period of a wave, calculated as 1/frequency
• Calculating wave period


  Time period = 1/frequency
• Wave period calculation


  • For a wave with frequency 50 Hz, the time period is 0.02 s
  • For a wave with frequency 400 Hz, the time period is 0.0025 s
• Wave speed


  Calculated as frequency x wavelength
• Calculating wave speed


  Wave speed = frequency x wavelength
• Wave speed calculation


  • For a wave with frequency 50 Hz and wavelength 6 m, the speed is 300 m/s
  • For a wave with frequency 0.2 Hz and wavelength 25 m, the speed is 5 m/s
• Longitudinal waves


  Waves where the vibrations are parallel to the direction of wave travel
• Compression


  An area of increased pressure where the particles are closer together than on average
• Rarefaction


  An area of reduced pressure where the particles are further apart than on average
• Demonstrating longitudinal waves


  Pushing and pulling a stretched slinky spring
• In longitudinal waves, the particles move backwards and forwards between compressions as the wave is transmitted through the medium, but none of the particles are transported along the wave
• Transverse waves are waves where the vibrations are perpendicular to the direction of wave travel
• Electromagnetic waves are transverse waves with a wide range of properties and uses
• Sound waves are longitudinal waves
• Transverse waves


  Waves where the vibrations are at right angles to the direction of wave travel
• Transverse waves


  • Ripples on the surface of water
  • Vibrations in a guitar string
  • A Mexican wave in a sports stadium
  • Electromagnetic waves - e.g. light waves, microwaves, radio waves
  • Seismic S-waves
• Transverse waves


  Can be thought of as 'shake' or 'shear' waves as the particles move from side-to-side - crossing the direction of wave travel
• Transverse waves


  • Energy is transferred from left to right, but none of the particles are transported along the wave
  • The particles move up and down as the wave is transmitted through the medium
• Electromagnetic waves are transverse waves with a wide range of properties and uses
• Sound waves are longitudinal waves
• Transverse waves


  Waves where the vibrations or oscillations are at right angles to the direction of wave travel
• Longitudinal waves


  Waves where the vibrations or oscillations are in the same direction as the direction of wave travel
• Electromagnetic waves


  Transverse waves caused by oscillations in an electromagnetic field
• Electromagnetic waves travel at 300 million metres per second (m/s) through a vacuum
• Electromagnetic spectrum


  A continuous series of waves arranged in order of wavelength or frequency
• Groups in the electromagnetic spectrum


  • Waves with very short wavelength, high frequency and high energy
  • Waves with very long wavelength, low frequency and low energy
• Visible light contains all the frequencies that can be detected by the human eye, with red light having the lowest frequencies and violet light having the highest frequencies
• Transverse waves


  Waves where the oscillation is perpendicular to the direction of wave propagation
• Longitudinal waves


  Waves where the oscillation is parallel to the direction of wave propagation