PHYSICS Q4

• Waves


  Properties of Waves
• Electromagnetic Waves


  • Radio wave
  • Microwave
  • Infrared
  • Visible light
  • Ultraviolet
  • X-ray
  • Gamma ray
• Electromagnetic Wave

  Waves propagated in the space from one region to another as a result of varying magnetic and electric fields
• Electromagnetic waves propagate at the speed of light, which is equal to 3.00 x 10 ^8 m/s
• Electromagnetic Waves


  • They have both electric and magnetic properties
  • Accelerating electrons produce them
  • They are a combination of electric and magnetic fields
  • A changing magnetic field produces an electric field and a changing electric field produces magnetic field
  • The electric field and the magnetic field oscillate perpendicular to each other and to the direction of the propagating wave
• JAMES CLERK MAXWELL predicted that waves could be propagated in the space from one region to another as a result of varying magnetic and electric fields

  1985
• Heinrich Hertz


  • He was the first to produce electromagnetic wave in the laboratory
  • He used an LC oscillator and a receiver
  • He proved that Maxwell's theory of electromagnetism is correct
  • The unit of frequency, hertz (Hz) is named in his honor
• Hertz's Experiment

  1. High voltage produced by the induction coil caused sparks to fly between the oscillator knobs

  2. The wave coming from these sparks induced in the current in the receiver producing the sparks between the receiver's end

  3. The waves generated oscillate at a frequency determined by the capacitance of the capacitor and the inductance of the induction coil

  4. The frequency of the waves produced by the Hertz corresponds to the radio frequency in the electromagnetic spectrum
• Electromagnetic waves


  Produced by magnetic and electric field oscillating perpendicular to each other to the direction of the wave propagation
• Electromagnetic spectrum


  • Radio wave
  • Microwave
  • Infrared
  • Visible light
  • Ultraviolet
  • X-ray
  • Gamma ray
• Photons


  Bundle of wave energy
• Wave


  A disturbance that travels through a medium and transfer energy from one place to another
• Mechanical wave


  • Propagate through a material medium (solid, liquid, or gas) at a wave speed which depends on the elastic inertial properties of that medium
  • Examples: sound waves, water waves, earthquakes / seismic waves
• Electromagnetic wave


  • Created as a result of vibrations between an electric field and a magnetic field
  • Do not need any medium for propagation
  • Velocity is 3.00 x 10 ^ 8 m/s
  • Examples: radio wave, microwave, infrared, visible light, ultraviolet, x-ray, gamma ray
• Transverse wave


  • The movement of the particles is at right angles or perpendicular to the motion of the energy
• Crest


  The peak or highest part of the wave
• Trough


  The lowest part of the wave
• Longitudinal wave

  • The movement of the particle is parallel to the motion of the energy, i.e. the displacement of the medium is in the direction in which the wave is moving
• Longitudinal wave


  • Sound waves
• Compression


  The regions of high pressure due to particles being close together
• Rarefaction


  The regions of low pressure due to particles being spread further apart
• Wavelength (λ)


  The distance between identical points in the adjacent cycles of crests of a wave. It is measured in meters.
• Amplitude (A)


  The height of the wave, usually measured in meters (m). It is directly related to the amount of energy carried by a wave, the greater the amplitude the energy.
• Frequency (f)


  The number of waves passing a point in a certain time. The unit of frequency is hertz (Hz) which is equal to one wave per second.
• Period (T)


  The time for a particle on a medium to make one complete vibrational cycle. As the period is time, hence is measured in units of time such as seconds or minutes.
• Wave speed


  1. v = λf

  2. v= λ/f
• Radio waves


  The longest wavelength in the EM Spectrum
• Radio waves


  • Electron vibrate in an antenna
  • Transmit sound and picture information over long distance
  • For communication purposes
• Wireless communication


  1908
• Guglielmo Marconi won the Nobel Prize for physics


  1909
• AM


  The amplitude of the high-frequency carrier wave is made to vary in proportion to the amplitude of the audio signal
• FM


  The frequency of the carrier wave is made to change in proportion to the audio signal's amplitude
• Applications of radio waves

  • Broadcasting
  • Mobile communication
  • Wifi
  • Bluetooth
  • Remote controls
  • GPS Navigation
• Microwaves


  Use in satellite communication, radar, & cooking
• James Clerk Maxwell discovered microwaves as part of his electromagnetic theory


  1864
• Microwave bands

  • C-Band
  • L-Band
• 1. Band


  • Medium length, penetrate through clouds, dust, smoke, snow, and rain to reveal the earth's surface
• 1. Band


  • Longer, Global positioning system, cover of forests to measure the soil moisture of rain forests
• Applications of microwaves


  • Satellite communication
  • Radar (Radio detection and ranging)
  • Doppler weather radar
  • Radar gun
  • Microwave oven
• Infrared


  Heat radiation