WaveFront, Wavelet, And Huygen's Principle


WaveFront:

It is defined as the focus of the particles in a homogeneous medium vibrating with some phase.

Types:

  1. Spherical wavefront
  2. Cylindrical wavefront
  3. Plane wavefront

1. Spherical Wavefront:

For a point source of light, locus of the particles vibrating with some phases is the
spherical surface and known as spherical wavefront.


2. Cylindrical Wavefront:

For linear source of light, locus of the particles vibrating with the same phase is the cylindrical surface and is called cylindrical wavefront.


3. Plane Wavefront:

For a source of light at infinity, locus of the particles vibrating with the same phase is the plane surface and known as plane wavefront.


Huygen's Principle

1. Every point on the wavefront acts as a new source of light and sends out disturbances in all possible directions similar to the original source. This gives origin of wavelet.

2. Tangential curve drawn on wavelets give new position of wavefront called secondary wavefront.

wavelets


Consider a pont source S and its original/primary wavefront XY as shown in the figure.

Take points a,b,c,... on this wavefront XY and according to huygen's principle, this point also acts as new source of light and sends out light waves in all posible direction . This gives origin of small spheres with centre at a,b,c...  called wavelets.

X'Y'  and X''Y'' are tangential curves drawn on wavelets called secondary wavefront.


# Applications
1. To verify laws of reflection of light.
2. To verty laws of refraction of light.

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