On the basis of Huygen's wave theory, prove Snell's law of refraction of light.
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Solution
Proof of Snell's law of refraction by Huygen's wave theory: Let speed of light in rarer medium be v1m/s and in denser medium, be v2m/s. So, DD′=v1t In the same time BB′=v2t In ΔBDD′sini=DD′BD′ ....(1) In ΔBB′D′sinr=BB′BD′ ......(2) Dividing equation (1) by equation (2), we get sinisinr=DD′BD′BB′BD′ sinisinr=DD′BB′ =v1tv2t sinisinr=v1v2=1μ2 i.e.,
1μ2=sinisinr
This is called Snell law of refraction. Hence, Snell's law is verified.