synapses

• AQA A-level Physics Waves Flashcards | Quizlet
• Waves are vibrations that transfer energy without matter
• Electromagnetic waves


  Oscillating electric and magnetic fields which progress through space without the need for a substance
• Electromagnetic spectrum


  • Radiowaves
  • Microwaves
  • Infrared radiation
  • Visible light
  • Ultraviolet
  • X-rays
  • Gamma rays
• Longitudinal waves


  Oscillate in the same direction as the wave travels
• Transverse waves


  Oscillate at 90 degrees to the direction of travel
• Displacement


  Distance from the undisturbed position
• Amplitude


  Maximum displacement from the undisturbed position
• Wavelength


  The distance between two corresponding parts of a wave
• Frequency


  Number of complete waves passing a point per second
• Period


  The time for one complete wave to pass a fixed point
• Wavespeed


  Frequency multiplied by wavelength
• Phase of a vibrating particle


  The fraction of a cycle it has completed since the start of the cycle
• Phase difference between 2 particles vibrating at the same frequency

  The fraction of a cycle between the vibrations of the 2 particles
• 1 cycle is equal to 360 degrees or 2 pi radians
• Intensity


  Amount of energy
• Units for


  • Wavelength: metres
  • Displacement: metres
  • Period: seconds
  • Frequency: Hertz
• Mechanical waves need particles to transfer energy created by physical oscillations of matter
• Longitudinal waves are always mechanical
• Electromagnetic waves do not need particles to transfer energy
• Plane-polarised


  Vibrations stay on one plane only
• Evidence for the nature of transverse waves: Polarisation
• Longitudinal waves cannot be polarised
• Transverse waves can be plane-polarised by passing them through a narrow slit
• If a 2nd slit is placed at 90 degrees to the 1st, it will block all wave energy from passing
• Plane of polarisation of an electromagnetic wave


  The plane in which the electric field oscillates
• Light from a lamp is unpolarised
• Use of polarisation: Polarised sunglasses to remove the glare of light reflected from water or glass
• Polaroid filters allow light to move in one direction only
• A polariser allows waves to pass through on one plane only
• Applications of polarisers: Polaroid material, alignment of aerials for transmission and reception
• Principle of superposition


  When 2 waves meet, the total displacement at a point is equal to the sum of the individual displacements at that point
• Stationary waves: Position of nodes & antinodes remain fixed
• Formation of stationary waves: When two or more progressive waves of the same frequency, travelling in opposite directions pass through each other
• Formation of stationary waves on a string in tension: Fix both ends & make the string vibrate
• Stationary waves formed from sound waves: Reflect at the ends & the reflected waves pass through each other
• In a pipe closed at one end, resonance occurs if there is an antinode at the open end and a node at the closed end
• Stationary waves in a tube with one open end: Node at closed end, antinode at open end
• Stationary waves in a tube with both ends open: Antinode at each end
• Stationary waves formed from microwaves: Form a stationary pattern when reflected by a metal plate back towards the transmitter