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| Verification of Laws of Refraction based on Huygen's Wave Theory |
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| XY is a plane surface separating a denser medium of refractive index from a rarer medium. If c1 and c2 are the velocities of light in rarer medium and denser medium then, |
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| 1m2 represents refractive index of medium 2 with respect to 1. |
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| Let AB be the incident plane wavefront. Let the wavelet B strike XY at A| in t seconds. |
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| In the same time t seconds, A travels in the denser medium with velocity c2 and covers a distance AB|= c2t. With A as centre and c2t as radius, draw an arc as shown. Repeat for points P and so on. The tangent to these arcs gives the reflected wavefront A|B|. One can prove that A|B| is the true refracted wave front by proving, |
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| BA|= BN + NA| |
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| = DP + NA| |
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| If one has to prove A|B| is the true wave front then it is sufficient to prove that |
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| or |
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| All the incident, normal and refracted rays lie in the same plane. |
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