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Waves

Science and art belong to the whole world, and before them vanish the barriers of nationality.

Goethe

Definitions to know:

  • A wave is a disturbance which moves through a medium.
  • The amplitude is the height of the wave.
  • The wavelength is the distance from one wave top, or crest, to the next.
  • The phase shift describes how far to the left or right the wave slides.
  • Rarefaction is the name given to the region where the coils of the spring are pulled apart.
  • Compression is the name given to the region where the coils of the spring are pushed together .
  • Frequency is the number of complete cycles in one second.
  • The period of a wave is the time taken for one complete cycle.
    .

Waves transmit energy without transmitting matter .

  • This means that waves can move energy from one place to another without moving any matter from one place to another .
  • The amount of energy which a wave has depends on its amplitude .

Most waves move through media (matter) but only move it backwards and forwards (longitudinal) or side to side (transverse) while the wave passes .

  • After the wave has gone, the matter is back where it started but energy has been carried by the wave from its origin (where it begins) to its destination (where it finishes).

One type of wave ( electromagnetic ) does not need any media to get it from its origin to its destination . It can travel through a vacuum ( nothing ) so these waves can travel from our sun other stars to Earth and other planets through space

Types of Waves:

  • 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. (up and down)

     

     

     

     

     

     

    • Longitudinal waves (sometimes called compressional waves) cause the medium to move parallel to the direction of the wave. (side to side)
      • Examples: sound, P-waves

       

       

       

     

     

     

     

    • Surface waves are both transverse waves and longitudinal waves mixed in one medium.
  • Electromagnetic waves do not require a medium to travel (light, radio).

Measuring Waves:

The wavelength can be measured as the distance between the center of two compressions, crests, or troughs.

The amplitude of the wave is measured from the crest (or trough ) to the mid-point .

Amplitude is a measure of how much energy the wave has.

Frequency is defined as the number of complete cycles in one second.

Hertz is the unit of frequency (symbol Hz ).
1 Hertz = 1 cycle per second .

The period of a wave is defined as the time taken for one complete cycle.

The period = 1 ÷ frequency .

 

 

Original Graphics Sources:

http://www.physics.ubc.ca/~outreach/phys420/p420_05/anthony/Transverse%20Waves.htm

http://www.gcsescience.com/a/pwav2.htm