InterviewSolution
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InterviewSolution
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A jar of height h is filled wih a transparent liquid of refractive index `mu`, Fig. At the centre of the jar on the botom surface is a dot. Find the minimum diameter of a disc, such that when placed on the top surface symmetrically about the centre, the dot is invisible. . |
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Answer» Let d be the diameter of the disc. The spot shall be invisible if the incident rays from the dot at O to the surface at d/2 at the criticale angle. Let `i` be the angle of inidence Using releatioship between refractive index and critical angle then, `" " sint =(1)/(mu)` ltbr Unsing geometry and trigonometry Now `" " (d//2)/(h)=tani` `rArr " " (d)/(2)=h tan i=h"["sqrt(mu^(2)-1)"]"^(-1)` `:. " " d=(2h)/(sqrt(mu^(2)-1))` This is the required expression of d. |
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