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A ray light of intensity I is incident o...


A ray light of intensity I is incident on a parallel glass-slab at a point A as shown in figure it undergoes partial reflection and refraction. At each reflection 25% of incident energy is refracted rays AB and A'B' undergo interference find the ratio `I_(max)//I_(min)`

Text Solution

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The correct Answer is:
`81:1`

As given reflection coefficient `=20%thereforeAB=(I)/(5)`
`A'B'=(16I)/(125)`
If AB and A'B' interference than
`I_(max)=(sqrt((I)/(5))+sqrt((16I)/(125)))^(2)=(I)/(5)xx(81)/(25)`
`I_(min)=(sqrt((I)/(5))-sqrt((16I)/(125)))^(2)=(I)/(5)xx(1)/(25)` ltbr. `thereforeI_(max)//I_(min)=81:1`
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