Waves

• What is a wave?

  A wave transfers energy and information without transferring matter.
• Transverse waves

  the direction of the oscillation is perpendicular to the direction of the energy transfer.
• Longitudinal waves

  the oscillation is parallel to the direction of energy transfer.
• What is amplitude?

  The maximum displacement from its undisturbed position.
• What is wavelength?

  The distance between the same point of 2 neighbouring waves.
• What is frequency?

  The number of complete waves passing a certain point each second. Measured in Hertz.
• What is the period?

  The time it takes for one full cycle of a wave. Period = 1/frequency.
• What is wave speed?

  The speed at which energy is being transferred.
• What is resolution?

  The smallest change measurable by the instrument.
• What happens when sound waves hit a solid?


  Air particles hitting the solid cause the particles in the solid to vibrate. These hit the next particles in line and so on passing the sound waves through the object as vibrations.
• What happens when a sound wave hits your ear?

  Ear drum vibrates when sound waves arrive.

  Ossicles and semicircular canals: tiny bones and canals that pick up and pass on vibrations.

  Cochlea turns vibrations into electrical signals that are sent to the brain.
• Why can't humans detect ultrasound?

  frequency is above 20,000Hz
• When ultrasound hits a boundary...

  some waves are transmitted at the boundary but some are reflected.
• What do earthquakes produce?

  Seismic waves which travel through the earth. They are detected on the surface with seismometers. Seismologists look for two things: how long the waves took to get there, which parts of earth's surface the waves never reached.
• P-waves

  Longitudinal so can travel through solids and liquids. Travel faster than S-waves. Refraction happens at the boundary.
• S-waves

  Transverse. Only travel through solids so can't travel through the molten outer core. No refraction