waves bbc bitesize

• Wave


  A disturbance that transfers energy from one place to another
• Examples of waves


  • Light
  • Sound
  • Ocean waves
  • Radio waves
  • Ultraviolet radiation
• Waves


  • All waves transfer energy from one place to another
• Types of waves


  • Transverse waves
  • Longitudinal waves
• Transverse wave


  A wave in which the particles move up and down at right angles to the direction it travels in
• Longitudinal wave


  A wave where the particles move forwards and backwards in the direction that the wave travels
• Frequency


  The number of vibrations of the wave in one second, also seen as the number of complete waves passing a point in one second. Frequency is measured in hertz (Hz).
• Wavelength


  The distance covered by a full cycle of the wave. Usually measured from peak to peak, or trough to trough.
• Amplitude


  The height of the top of a wave from its resting position. The greater the amplitude, the taller the wave (and the louder the sound if a sound wave).
• Oscillation


  A wave oscillates, which means it moves backwards and forwards or up and down in a regular, repeating way.
• Peak


  The highest point of a transverse wave
• Trough


  The lowest point of a transverse wave
• Compression


  A region of high pressure, where the particles are closer together than normal
• Rarefaction


  A region of low pressure, where the particles are further apart than normal
• Time period


  The time taken for one complete cycle of the wave. It is also the time taken for one complete wave to pass by
• Displacement-distance graphs can be used to measure and compare the wavelength of a wave
• Displacement-time graphs demonstrate how the displacement of one point on the wave varies over time
• Displacement-time graphs can be used to compare the frequency of different waves
• A sound wave is a vibration that travels through a solid, liquid or gas such as the air or water
• Loud sound


  Has a large amplitude
• High pitched sound


  Has a high frequency
• Musicians and scientists record and analyse sounds using wave traces
• How sound waves are made

  1. Something shakes or vibrates

  2. Vibrations are passed on between air particles

  3. Particles vibrate in the same direction as the wave travels
• Sound waves


  • Are longitudinal waves where particles move forwards and backwards in the direction the wave travels
• Loudness


  Measure of how humans hear sound intensity, measured in decibels (dB)
• If air particles move back and forth a lot


  We hear a loud sound
• If the source of a sound makes the particles vibrate more gently


  We hear a quieter sound
• Pitch


  How high or low a sound is, depends on how quickly the air vibrates
• Frequency


  Number of vibrations per second, measured in hertz (Hz)
• The lowest pitch sound most humans can hear is 20 Hz, the highest is 20,000 Hz</b>
• Wave trace


  A graph that can be used to compare the pitch and loudness of a sound
• Wave traces


  • Appear as transverse waves but are actually longitudinal sound waves
  • Show the size of the air particle vibrations on the vertical axis against time on the horizontal axis
• Loud sound


  Makes the air move back and forth a lot, so the wave trace peaks are big
• Quiet sound


  Makes the air vibrate back and forth less, so the wave trace peaks are smaller
• High pitch sound


  Has a high frequency, so the wave trace peaks are closer together
• Low pitch sound


  Has a low frequency, so the wave trace peaks are further apart
• Amplitude


  The height of the wave trace peaks from the resting position