Waves updated

• Wave

  • A periodic disturbance in a solid, liquid or gas as ENERGY is transmitted through the medium.
  • CARRIES THE ENERGY through the matter or space
• Medium

  • A physical environment in which phenomena occur
  • The matter through which a wave travels
• Mechanical Wave

  • A wave that requires a medium.
  • CanNOT travel through a vacuum.
  • Almost ALL waves
• ELECTROMAGNETIC WAVES

  • Can travel across EMPTY space.
  • Does NOT require a medium
  • Consists of changes in electric and magnetic fields in space. 
  • Visible light  and RADIO waves are just 2 examples
• Things that waves do

  • Waves transfer energy
  • Waves can do work.  (because work is the transfer of energy)
  • Sound waves do work on your ear drum
  • Light waves do work on your eyes
• Waves

  • WAVE MOTION TRANSFERS ONLY ENERGY, NOT MATTER

  Mechanical waves are transferred by the motion of particles, but NO MATTER is transferred.
• What happens to the wave?


  Mechanical waves spread out through the medium evenly and sphereically from the source, if the area is open in ALL directions.  The stronger wave will be in the direction of the source
• LONGITUDINAL WAVES

  • Have parallel motion
  • A wave in which the particles of the medium vibrate parallel to the direction of the wave motion.
• TRANSVERSE WAVES

  • Have perpendicular motion
  • A wave in which the particles of the medium move perpendicular to the direction of the wave motion
• Types of Waves


  Mechanical Waves and Electromagnetic
• Forms of Mechanical Waves

  Longitudinal waves and transverse waves
• Form of electromagnetic waves

  Modeled as transverse
• Medium of longitudinal waves Solids, liquids, gases
• Mediums of Longitudinal waves


  Solids, liquids, gases
• Mediums of Transverse waves


  solids and liquids
• Medium of electromagnetic waves

  none required
• description of longitudinal waves

  compressions and rarefactions in matter
• description of transverse waves


  Back-and-forth (up-and-down) movement of matter
• description of electromagnetic waves


  oscillating electric and magnetic fields
• Examples of longitudinal waves

  sound waves, shock waves, seismic P waves, some earthquake waves
• Examples of transverse waves


  water waves, rope waves, some earthquake waves,
• Examples of electromagnetic waves

  visible light waves, radio waves, X-rays
• Amplitude

  • the maximum distance that the particles of a wave’s medium vibrate from their rest position
  • Half the vertical distance b/w crest and trough
  • more energy = bigger amplitude
• Longitudinal waves

  • do not have crests or troughs
  • Compressions = crowded areas, comparable to crests
  • Rarefactions = stretched out areas, comparable to troughs
• Wavelength

  • The distance from any point on a wave to an identical point on the next wave.
  • Represented by Greek symbol→ lambda λ
  • From CREST to CREST or TROUGH to TROUGH

  UNITS: meters
• Period

  • The time it takes a complete cycle or wave oscillation to occur
  • The time it takes for 1 wavelength to pass a specific point.  
  • Expressed in seconds
  • Symbol: T
• Frequency

  • The number of full wavelengths that pass a point in a given time interval
  • Measured in hertz (Hz)
• The Electromagnetic Spectrum

  • The part of the spectrum that is visible to the naked eye is called visible light.  
  • It ranges from Infrared to ultraviolet
  • Infrared has a long wavelength, whereas ultraviolet has a short wavelength.  
  • Electromagnetic waves also exist at other frequencies.  
• Wave Speed

  • How fast a wave moves.
  • The speed of a moving object is found by dividing the distance traveled by the time it takes to travel that distance.
  • V=d/t
• Wave Speed

  • For a wave it is convenient to use the wavelength as the distance traveled
  • the amount of time it takes for 1 wavelength is a period$v=$$λ/T$ $v=$$fλ$
• SPEED DEPENDS ON MEDIUM GAS

  • Sound can travel through air.  If they couldn’t you would not be able to have a conversation with your friend.  
  • Sound travels very fast, so you don’t notice the delay.  (v=340m/s)
• SPEED OF SOUND IN WATER

  • Sound travels better and 3-4x faster in water and farther.  
  • Dolphins can communicate over long distances in water
• Sound in Solids

  • Sound waves travel even faster in solids.
  • Move up to 15-20 faster in rock or metal.
• Summary

  • The speed of a wave depends on the medium.
  • But in that medium the speed of the wave is CONSTANT
  • The speed of the wave in a medium doesn’t depend on the frequency of the wave, it travels as fast, just more often. 
• • In gases, the molecules are far apart and mover randomly, therefore the wave must travel through a lot of empty space before “bumping” into another particle.
  • (NOT ELECTROMAGNETIC/LIGHT WAVES)
• • In liquids, such as water, the molecules are much closer together, but they are still free to slide past one another.  
  • Vibrations are transferred more quickly.
• • In solids, molecules are not close together, but are tightly bound
  • When 1 mass vibrates, all of the particles vibrate.
  • This causes MECHANICAL waves to travel very quickly through solids.  
• Pitch

  • How high or low the sound is.  
  • Determined by the frequency at which the wave hits the eardrum
  • High Pitch = High frequency
  • Low Pitch = Low frequency
• Sound of a stationary object

  • Sound waves spread out evenly in a 360-degree direction.
• Doppler Effect, stationary, moving

  • When the source of the sound is moving, the waves (in the direction of the movement) get compressed, increasing the frequency, increasing the pitch