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Plane & cylindrical wavefront

  1. Sep 2, 2013 #1
    1.how and why does a light source in an isotropic medium at INFINITY produces PLANE Wavefronts instead of CIRCULAR Wavefronts as in case , when a light source is in the same isotropic medium but at FINITE distance?

    2.how and why does a linear source of light such as a slit illuminated , produces CYLINDRICAL waves?
  2. jcsd
  3. Sep 2, 2013 #2
    1. Spherical wavefronts change into plane wavefronts at infinity, because the radius of the sphere grows with the distance. A sphere with infinite radius has zero curvature: it is a plane.

    2. This is caused by diffraction.
  4. Sep 6, 2013 #3

    Claude Bile

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    Science Advisor

    We can describe any (scalar) field as a linear sum of harmonic functions, be they planar (cartesian), cylindrical or spherical.

    For example, a plane wave can be described as a sum of cylindrical harmonics. A cylindrical harmonic can conversely be described as a sum of plane waves.

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