WBCS Preliminary (Physics): Waves

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  • WAVES: There are three types of waves:

    1. Mechanical waves require a material medium to travel (air, water, ropes). These waves are divided into three different types.
      • Transverse waves cause the medium to move perpendicular to the direction of the wave.
      • Longitudinal waves cause the medium to move parallel to the direction of the wave.
      • Surface waves are both transverse waves and longitudinal waves mixed in one medium.
    2. Electromagnetic waves do not require a medium to travel (light, radio).
    3. Matter waves are produced by electrons and particles.
  • A point of maximum positive displacement in a wave, is called crest, and a point of maximum negative displacement is called trough.
  • Measuring Waves: Any point on a transverse wave moves up and down in a repeating pattern. The shortest time that a point takes to return to the initial position (one vibration) is called period, T.
  • The number of vibrations per second is called frequency and is measured in hertz (Hz). Here's the equation for frequency: f = 1 / T
  • The shortest distance between peaks, the highest points, and troughs, the lowest points, is the wavelength, λ.
  • By knowing the frequency of a wave and its wavelength, we can find its speed. Here is the equation for the velocity of a wave: v= λf.
  • However, the velocity of a wave is only affected by the properties of the medium. It is not possible to increase the speed of a wave by increasing its wavelength. By doing this, the number of vibrations per second decreases and therefore the velocity remains the same.
  • The amplitude of a wave is the distance from a crest to where the wave is at equilibrium. The amplitude is used to measure the energy transferred by the wave. The bigger the distance, the greater the energy transferred.


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