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Wave Optics Explain the use of wavefront to understan wave propagation. |
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Answer» Solution :Principle : Every point or particle of a wavefror behave as an independent secondary SOURCE an emits by itself secondary spherical waves. After very small time interval the surface tangential t all such secondary spherical wavelets give th position and shape of new wavefront. BASICALLY the Huygen.s principle is a geometri construction. SUPPOSE, that `F_(1),F_(2)` represents a part of spherica wavefront at t = 0 which is a wave propagating outwards.  According to Huygen.s principle all points of this wavefront `(F_(1)F_(2))` (A, B, C, ...) behave as secondary sources and velocity of wave is v, then distance covered in time `tua` is `vtau`. To determine the shape of wavefront at `t=tau`, draw SPHERES of RADIUS `vtau`from each point on the spherical wavefront and draw a common tangent to all these sphere then at time t after `tau` time gives the position and shape of new wavefront which is `G_(1)G_(2)`in the forward direction. This is a spherical wavefront with centre O and `D_(1)D_(2)` spherical wavefront is found backward. The points A., B., C. on `G_(1)G_(2)` act as secondary source. |
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