# Hugyens principle

1. Nov 5, 2007

### pardesi

can someone explain that i really don't make any real sense or use out of it

2. Nov 5, 2007

### Retsam

Hugyen's principle just says that any point on a wavefront can be thought of as a new point source of waves. Thus along a wavefront there are an infinite number of points all emitting sphereical waves. The interference from these secondary wavelets constructs a new wave front ahead of the first, and so on, allowing the wave to propogate through space. Ofcourse this does not really happen, it is just a way to model the situation, one drawback of this theory is that the point sources emit waves radially and so some of the waves are directed in the opposite direction to wave propagtaion, causing interference. So as you can see it is only an idea, not a reality.

3. Nov 5, 2007

### cesiumfrog

Not even for the case of, say, sound waves through a solid?

4. Nov 5, 2007

### pardesi

yes i got that part but is there any point in 'using' it.I really don't get the crunch of the situation and rather feel it narrows down the meaning of a wave.

5. Nov 7, 2007

### Claude Bile

Huygens' principle is used in the derivation that relates the Fourier transform of an aperture function to its far-field diffraction pattern, so to gain a full appreciation of how Huygens' principle fits in to diffraction theory - and not just as a hand-waving argument, I suggest looking up this derivation and seeing how Huygens' principle forms a crucial step.

Huygens' principle however is not 100% accurate (as it does not predict the existence of evanescent waves for example). A more rigorous version of Huygens' principle regards a wave as the sum of a series of infinite plane waves with varying amplitudes, with each plane wave possessing a single propagation constant (much the same way a sine wave possesses a single frequency).

Claude.