diffraction

diffraction

1. spreading of waves when they pass through a gap or by an edge

2. diffraction of water waves through a gap

   • shown by a ripple tank
     • diffracted waves spread out more if:
       • the gap is made narrower
       • the wavelength is made larger

3. diffraction of light by a single slit

   • directing a parallel beam of light at a slit
     • pattern shows
       • central fringe with further fringes either side of the central fringe
       • intensity of the fringes is greatest at the centre of the central fringe
       • central fringe - x2 wide as each of the outer fringes
       • peak intensity of each fringe decreases withy distance from the centre
       • each of outer fringes - same width
         • less intense than the central fringe

4. more about single slit diffraction

   • different sources of monochromatic light
     • greater the wavelength, the wider the fringes
   • using adjustable slit
     • narrower slit, wider fringes

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