InterviewSolution
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InterviewSolution
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A transparent sphere of radius R ahs a cavity of radius `R//2` as shown in figure,. Find the refractive index of the sphere if a parallel beam of light falling on left sureface focuses at point P. |
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Answer» Correct Answer - `(3+sqrt(5))/(2)` Let refractive index of glass be `mu` Let after first refraction, image distance be v, then `(mu)/(v)-(1)/(oo)=(mu-1)/(R)rArrV=(muR)/(mu-1)` Now second refraction will take place. So distance of first image from O is `mu_(1)=(muR)/(mu-1)-R=(R)/(mu-1)` and image is formed at R. `(1)/(R) -(mu(mu-1))/(R)=(2(1-mu))/(R)rArr mu^(2)-3mu+1=0` So`mu=(3+sqrt(5))/(2)` |
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