superposition and interference

• Coherent waves will vibrate with the same frequency and with constant phase difference.
• Interference is the name given to the superposition of waves from two coherent sources. Constructive interference is where waves are in phase. destructive interference is where waves are in anti-phase.
• newton said light is found in corpuscles (little packets of light) and is a particle.
• Huygens said light is a wave.
• Coherent sources emit light waves at the same frequency with constant phase difference.
• Youngs practical requires the following to work;

  • light needs to be coherent
  • laser light needs to be coherent / monochromatic and in phase
  • normal light needs a filter
  • the first slit makes light monochromatic
  • two slits stimulate two sources.
• A diffraction grating has 1000 lines per mm.
• the interference pattern produced from a diffraction grating is as follows; is the result of the superposition of the diffracted waves with a zero order maximum. with a following pattern of orders.