Revision Answers

  1. Use the wave equation v = wavelength x frequency.
    Now the speed v is the speed of light since all electromagnetic waves, which include radio waves, travel at the speed of light in air, which is 3 x 108m/s.
    Putting in the numbers gives
    3x 108 = wavelength x 810,000
    3x 108 / 810,000 = 370m
  2. The classic example is thunder and lightning. Thunder and lightning occur at the same time but when watching the storm from afar you see the lightning first before the sound.
    This is because the speed of light travels much much faster than the speed of sound.
    Another striking example can be found on the golf course. If you are watching a distant golfer you see him swing his club and after a second or so you hear the whack of the club on the ball!
  3. Use the equation distance = speed x time
    Since it is the sound of the strike we hear, we have to use the speed of sound in air. So the speed of sound in air = 340m/s.
    This gives us distance = 340m/s x 1.5s
    distance = 510m
  4. radiodishThe weak radio signals strike the radio dish and are reflected onto the detector. As seen from the diagram the signals are focused onto the detector.



  5. On the diagram below A, B, C are all wavelengths. D & E are amplitudes of the wavewavediagram











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