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Define term, "refreactive index " of a medium. Verify Snell's law refraction when a plane wavefront is propagating from a denser to a rarer medium. |
Answer» Solution :Refrative Index : REFRACTIVE Index is the ratio of the sine of angle of incidence to the sine of the angle of refraction.  `1mu_(2)`is the refractive index of 2nd MEDIUM w.r.t. Ist medum. Laws of refraction of the basis of Huygen's wave theory : Let PP' represents the medium (1) and medium (II). Let `v_(1)" and "v_(2)` represent the speed of light in medium (I) and medium (II) respectively. Let AB be the incident wave front and EC be the refracted wave front.  `BC==v_(1)t,""AE=v_(2)t` `"In "DeltaABC, sini=(BC)/(AC)=(v_(1)t)/(AC)"....(1)"` `"In "DeltaCAE, sin r=(AE)/(AC)=(v_(2)t)/(AC)"....(2)"` Dividing equation no. (1) and (2) `(sini)/(sinr)=(v_(1)t)/(AC)xx(AC)/(v_(2)t)=v_(1)/v_(2)="CONSTANT"` Let C be the speed of light `mu_(1)=c/v_(1)"rArr"v_(1)=c/mu_(1)"...(3)"` `mu_(2)=c/v_(2)"rArr"v_(2)=c/mu_(2)"...(4)"` Dividing equation (3) and (4) `v_(1)/v_(2)=mu_(2)/mu_(1)=(sini)/(sinr)` `mu_(2)sinr=mu_(1)sini.` This proves the Snell's law of refraction. |
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