stuff i need to remember p6..

• • wavelength: distance between the same point on 2 adjacent waves
  • amplitude: maximum displacement from rest
  • frequency: number of waves that pass a point per second
  • period: time taken for a full cucle of waves to pass a point
• v=fλ

  velocity/wavespeed= frequency x wavelength
• TRANSVERSE WAVES

  • have peaks & troughs
  • vibrations are perpendicular to direction
  • eg: all EM waves, light, waves in water
• LONGITUDINAL WAVES

  • have compressions & rarefactions
  • vibrate parallel to direction
  • eg sound waves
• MEASURING VELOCITY: OSCILLOSCOPE

  1. set up oscilloscope so detected waves are separate
  2. start with both mics next to speaker then slowly move one away until 2 waves are aligned but have moved 1 wavelength apart
  3. measure distance between mics= wavelength
  4. use v=fy to find spd_ f= wtv u set signal generator to
  5. spd of sound aprox 330m/s so check results agree with that
• MEASURING VELOCITY: RIPPLE TANK

  1. using signal generator attached to dipper & create waves at set frequency
  2. distance between each shadow = 1 wavelength_ measure 10 & divide by 10 to find average wavelength
  3. v=fy calculate speed

  • good method for measuring small wavelengths & moving waves
  • suitable because allows you to measure wavelength without disturbing waves
• MEASURING VELOCITY: STRING

  1. turn on signal generator and vibration transducer
  2. adjust frequency of generator until theres a clear wave on the string_ frequency depends on LENGTH of string between pulley and transducer and MASSES used
  3. measure 4-5 half wavelengths and divide to get mean HALF WAVELENGTH (double to get mean full wavelength)
  4. v=fy to find speed
• • wave is ABSORBED by second material; transferring energy to material’s energy store_ often thermal
  • wave is TRANSMITTED through second material— carries on travelling through new material; often leads to REFRACTION
  • wave is REFLECTED; ‘sent back’ from second material
• EM WAVES

  • transfers energy from SOURCE to ABSORBER
  • travel at SAME SPEED through air or vacuum
  • EM waves are vibrations of ELECTRIC AND MAGNETIC FIELDS = can travel through a vacuum
• EM WAVES

  (long wavelength, low frequency)

  radio waves

  microwaves

  infrared

  visible light

  ultraviolet

  X-rays

  gamma rays

  (short wavelength, high frequency)
• EM WAVES

  • our eyes can only detect visible light
• EM WAVES

  • large range of frequencies because EM waves are generated by a variety of changes in atoms & nuclei
• REFRACTION: waves changing direction at a boundary

  • when a wave crosses a boundary, it changes speed
  • if wave hits boundary at angle, it CHANGES DIRECTION- it’s refracted

  OPTICAL DENSITY: how quick light travels through_ high density material = slow travel

  • the wave bends TOWARDS the normal if it SLOWS down (= dense)
  • bends AWAY form normal if less dense; wave speeds up
  • WAVELENGTH changes when refracted, FREQUENCY STAYS THE SAME