Explain the limitation of the Huygens-Fresnel principle. What are the two crucia

Question

Explain the limitation of the Huygens-Fresnel principle. What are the two crucial factors that need to be introduced “by hand” in the equations to make the calculated diffraction pattern relevant to reality?

Consider a test body in a circular orbit in the equatorial (? = ?/2) plane of a Kerr black hole-a rotating, uncharged black hole. Find the energy per unit mass E and the azimuthal angular momentum per unit mass of the body, in terms of the coordinate components t and ? of its four-velocity. In coordinates (t,r,0.0) similar to Schwarzschild coordinates known as Boyer-Lindquist coordinates for this geometry), the spacetime outside the rotating hole has metric p2 with Mc' where S is the spin angular momentum of the hole. HINT: Use the geodesic Lagrangian method. The t and ? components of the geodesic equation for the orbiting body are easily integrated

Explanation / Answer

The Wavefront principle could not explain the deviations from rectilinear propagation that occur when light encounters edges, apertures and screens, commonly known as diffraction effects. Huygens theory does not account for the non existanca of a backward wave.

The resolution of this error was finally explained by David A.B. Miller in 1991. The resolution is that the source is a dipole (not the monopole assumed by Huygens), which cancels in the reflected direction.

To obtain agreement with experimental results, he had to include additional arbitrary assumptions about the phase and amplitude of the secondary waves, and also an obliquity factor.

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