Wavefronts & Rays (HL IB Physics)

• Waves can be represented graphically in two different ways:
  • Wavefronts - lines joining all the points that oscillate in phase and are perpendicular to the direction of motion (and energy transfer)
  • Rays - lines showing the direction of motion (and energy transfer) of the wave that are perpendicular to the wavefront

Wavefronts and rays for transverse waves travelling in a horizontal plane

• Wavefronts from above will therefore just look like a series of vertical lines

Waves can be represented using wavefronts

• The distance between successive wavefronts is equal to the wavelength of the waves

•  Wave phenomena such as reflection can be shown through rays, or the wavefronts
  • Notice the ray is still always perpendicular to the wavefronts

Reflection can be shown through rays or wavefronts

• Ripple tanks are used a common experiment to demonstrate diffraction of water waves

 

Wave effects may all be demonstrated using a ripple tank

 

• The diagram below shows how the wavelengths differ with frequency in a ripple tank
  • The higher the frequency, the shorter the wavelength
  • The lower the frequency, the longer the wavelength

 

Ripple tank patterns for low and high frequency vibration