Waves

• Longitudinal waves

  • How do they travel
  • Example

  They travel parallel to the direction of travel

  Sound
• Transverse waves

  • How do they travel
  • examples

  They travel perpendicular to the direction of travel

  Light waves and electromagnetic waves
• Speed =

  Frequency =

  Speed = Frequency x wavelength

  Frequency ( measured in Hertz or Hz) = 1/ time period
• Reflection

  When does it occur?

  What happens to frequency, speed and wavelength

  All waves can be reflected

  The angle of incidence is equal to the angle of reflection

  They all stay the same
• Range of audible frequency's for humans

  20Hz - 20,000Hz
• Measuring speed of sound

  1. Make a sound a large distance away from a solid wall

  2) Measure time taken for echo to be heard

  3)Then use speed= distance over time where distance is x2 the length from the wall as it travels there and back
• Oscilloscope

  Oscilloscope can be connected to a microphone to display sound waves used to measure amplitude and frequency

  Greater amplitude = greater noise (louder)

  Greater Frequency = Greater pitch
• Electromagnetic spectrum

  Order

  Similarities

  They all travel at the same speed in a vacuum and similar speeds in air

  • Radio waves- Red - Radio and television communications Reflected in the layer of the ionosphere

  Microwaves- Orange - Satellite transmissions ,cooking - Penetrates the ionosphere

  Infrared waves- Yellow - Heaters night vision

  Visible light- Green - Fibre optics and photography
• Electromagnetic spectrum 2

  Ultra Violet - fluorescent lamps

  X-rays - medical imaging , security

  Gamma rays - Sterilising food and medical equipment
• Total internal reflection

  When does it occur

  What are the conditions?

  Equation?

  Occurs when the angle of incidence is greater then the critical angle and light reflects back into the medium

  Light must travel from a more optically dense medium to a less optically dense medium

  n=1/sin (c)
• Optical Fibres

  Description

  When is it used

  Long thin rod of glass surrounded by cladding that uses Total internal reflection to transfer information through light even when bent

  It can be used in endoscopes in medical field

  It can be used in high speed data transfers in communication
• Refraction

  When does is occur

  How is speed wavelength affected

  Snell's law

  Occurs when the speed of a wave changes as it enters a new medium

  Denser medium - Speed decreases and bends towards the normal

  Less dense medium - Speed increases and bends away from the normal

  Frequency stays the same but Wavelength changes

  Snell's law- Angle of incidence is greater then angle of refraction

  N = sin (i)/ sin (r)
• Waves definition

  Transfer energy and information without the transfer of matter

  Particles oscillate about a fixed point
• • Amplitude
  • Wavefront
  • Frequency
  • Time period

  Amplitude - Distance from equilibrium to maximum displacement

  Wavefront - Two same points of a wave

  Frequency - Number of waves that pass through a single point per second

  Time period - Time taken for one complete wave to pass through a fixed point
• Doppler effect

  Definition

  How is pitch and frequency changed when object is moving towards the observer

  If a wave source is moving relative to an observer there will be a change in the observed frequency and wave length due to the doppler effect

  Because the wavefronts either get bunched up or spaced apart

  When an object is moving closer to the observer the frequency of the wave is increased as the wave fronts are bunched together meaning that the number of waves that pass a single point per second will increase.

  The pitch also increases