Physics - Waves

• Properties of all waves

  • Wavelength
  • Frequency
  • Amplitude
  • Speed
• Wavelength (λ)


  The distance from one peak to the next
• Frequency (f)


  How many complete waves there are per second (passing a certain point), measured in hertz (Hz)
• Amplitude


  The height of the wave (from rest to crest)
• Speed (v)


  How fast the wave goes
• Period (T)

  The time it takes (in s) for one complete wave to pass a point
• Speed of light is 3 x 10^8 m/s
• Wave Speed

  Speed = Frequency x Wavelength
• Transverse waves


  Waves where the vibrations are at 90° to the direction energy is transferred
• Transverse waves


  • Light and all other EM waves
  • A slinky spring wiggled up and down
• Longitudinal waves


  Waves where the vibrations are along the same direction as the wave transfers energy
• Longitudinal waves


  • Sound and ultrasound
  • Shock waves, e.g. some seismic waves
  • Waves on strings
  • Ripples on water
• Vibrations in transverse waves are from side to side
• Vibrations in longitudinal waves are in the same direction as the wave is travelling
• All waves transfer energy and information without transferring matter
• All waves carry and transfer energy in the direction they're travelling
• Energy transfer by waves

  • Microwaves in an oven make things warm up
  • Sound waves can make things vibrate or move, e.g. loud bangs can start avalanches
• Waves can be used as signals to transfer information from one place to another
• Information transfer by waves


  • Light in optical fibres
  • Radio waves travelling through the air
• Parts of a wave

  A) Crest

  B) Trough

  C) Amplitude

  D) Wavelength

  
• A wavefront is an imaginary plane that cut across all the waves, they connect points on adjacent waves which are vibrating together.
• The doppler effect :

  • Waves produced by a source which is moving towards or away from an observer sounds different than they would if it was stationary. This is because the waves have a different wavelength because the source is moving, the waves "catchup" or spread out, depending on the direction.
  • Waves moving towards you will have a shorter wavelength and a higher frequency
  • Waves moving away from you will have a longer wavelength and a lower frequency
• Electromagnetic Spectrum

  A) Radio

  B) Microwave

  C) Visible

  D) Uv

  E) X-ray

  F) Gamma Ray

  G) 10^-10

  H) 0.5X10^-6

  I) 10^-5

  J) 10^-2

  K) 10^3

  
• Colours :

  • Red longest wavelength
  • Violet shortest wavelength
• EM Spectrum and their uses :

  • Radio Waves - Communication
  • Microwaves - Satellite Communication and Heating Food
  • Infrared - Heating and Monitoring Temperature
  • Visible - Photography
  • Ultraviolet - Fluorescent Lamps
  • X-rays - See bones
  • Gamma - Sterilizing Food and Medical Equipment
• EM Spectrum and their dangers :

  • Microwaves - can heat human tissue
  • Infrared - can give nasty skin burns
  • UV - can damage surface cells and cause blindness
  • Gamma - can cause cell mutilation or destruction, leading to cancer or tissue damage
• All waves in the Electromagnetic Spectrum are a transverse waves
• Angle of Incidence = Angle of Refraction
• Light is refracted because different mediums have different speeds.
• The ray that exits the medium is known as The Emergent Ray
• Snell's Law Refractive Index Formula

  n = Sin(i)/Sin(r)
• Snell's Law Critical Angle Formula

  SinC = 1/n
• refractive index formula including speed of light of vacuum and in that material


  n = Speed of light in a vacuum (c) / Speed of light in that material (v)
• light going from a higher refractive index to a material with a lower refractive index speeds up and so bends away from the norma;
• What is Total Internal Refraction?

  It is when the angle of incidence is equal to or more than the critical angle. No light leaves the medium.
• Uses of Total Internal Refraction :

  • Optical Fibers
  • Used in prism in periscope of a submarine
• Sound waves are longitudinal waves caused by vibrating objects.
• The human ear is capable of hearing sounds from 20hz to 20,000hz
• Because sound waves are caused by vibrating particles, the denser the medium, the faster it will travel.
• Greater Amplitude = Louder