NEET Sample Paper NEET Sample Test Paper-27

  • question_answer
    Light passes through a glass plate of thickness d and refractive index \[\mu \]. For small angle of incidence \[\theta ,\] the lateral displacement will be:

    A)  \[d(\theta )\]              

    B)  \[d\,(\theta )\,\,(\mu -1)\]

    C)  \[d\,(\theta )\,\mu /\mu -1\]                 

    D)  \[d\,(\theta )\,\frac{(\mu -1)}{\mu }\]

    Correct Answer: D

    Solution :

    Suppose the displacement be x: Then         \[\left( \frac{x}{l} \right)=i-r\] Also,         \[\left( \frac{d}{l} \right)=\cos r\] As i is small, so r is also small, hence             \[\left( \frac{d}{l} \right)\approx 1\] i.e.         \[d\approx 1\] Therefore        \[\frac{x}{d}=i-r\]                         \[x=di\,\,\left( 1-\frac{x}{i} \right)\] Also, for small angles             \[\frac{\sin i}{\sin r}\approx \frac{i}{r}=\mu \]             \[x=di\,\left( 1-\frac{1}{\mu } \right)\] Put \[i=\theta ,\] we get \[x=\frac{d\theta (\mu -1)}{\mu }\]


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