5.5 - Interference

5.5 - Interference

1. Coherence

   • Same frequency
   • Constant phase difference
   • Light from 2 different sources can't create a fringe pattern as they are not coherent

2. Wavelength and Colour

   • Red has the greatest wavelength
     • Fringe separation is greater in red light due to this.
   • Blue/purple have the shortest wavelengths
   • White Light
     • Composed of a continuous spectrum of different wavelengths
     • White Light Fringes
       • Blue light fringes are closer due to smaller wavelength
       • Red light fringes are further apart due to greater wavelength
       • Central white fringe due to every colour contributing
   • Longer wavelength, greater fringe separation

3. Laser Light

   • Monochromatic
     • Very specific wavelength
   • Source of coherent light
     • Photons in a laser are in phase.
   • Very intense
     • May damage retina of the eye
       • Wear laser protective goggles
       • Don't direct laser at people

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