Wave Motion and Interference: Key Terms and Path Difference

Wave Motion

1. Progressive Waves

   • Waves that travel through a material or vacuum and that transfers energy from one position to another

2. Longitudinal Waves

   • the particles of the medium vibrate parallel to the direction of the wave velocity

3. Transverse Waves

   • the particles of the medium vibrate at right angles to the direction of wave velocity

4. Wavelength- the distance between two successive peaks or troughs

5. Displacement- the distance of a point on the wave from its undisturbed position

6. Amplitude- the maximum displacement at a peak or trough of the wave

7. Period- the time taken for one complete oscillation of a point in a wave

8. Frequency

   • Frequency= 1/ time period
   • Frequency- the number of oscillations per unit time Unit: Hz

9. Path Difference

   • the extra distance travelled by one of the waves compared with the other
   • Constructive Interference
     • The path difference is a whole number of wavelengths
       • Path Difference = 0,1 X Wavelength, 2 X Wavelength, 3 X Wavelength
         • Path Difference = n X Wavelength
   • Destructive Interference
     • The path difference is an odd number of half wavelengths
       • Path Difference= 0.5 X Wavelength, 1.5 Wavelength, 2.5 Wavelength,
         • Path Difference= [n + 0.5 ] Wavelength

10. Phase

    • the position of a point in time [instant] on a waveform cycle
      • In Phase = phase difference of 0 degrees
        • In anti-phase= phase difference of 180 degrees

11. Coherence- coherent sources emit waves that have a constant phase difference