Wave Nature of Light: Hygens' Principle

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Wavefront: A surface in a medium on which all particles are in the same phase of oscillation. Ray: A line drawn normal to the wavefront giving the direction of propagation of the wave. In a homogeneou…

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A spherical wavefront is produced when light comes from a point source and spreads in all directions. The rays are radial lines. Amplitude varies as 1/r and intensity varies as 1/r^2.

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A plane wavefront is formed when light travels in one direction and the particles on a plane surface are in the same phase. The rays are parallel straight lines. For a plane wavefront, amplitude and i…

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A cylindrical wavefront is produced by a line source, such as a fine rectangular slit. The wavefront has cylindrical shape with the source as axis. For a cylindrical wavefront, amplitude A ∝ 1/√r and …

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1) Every particle of the medium situated on the wavefront acts as a new wave-source from which fresh waves originate. These waves are called secondary wavelets. 2) The secondary wavelets travel in the…

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Newton's corpuscular theory explained some phenomena, but interference, diffraction and polarisation remained unexplained. These three phenomena support wave nature of light.

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Huygens' wave theory explains all the observed phenomena of light, including reflection, refraction, interference, diffraction and polarisation. It gives a geometrical construction for wavefront propa…

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A wavefront from a distant star is spherical, but the star is very far away. So the small portion intercepted by Earth has very large radius and behaves like a plane wavefront.