An observer can see through a pin–hole the top end of a thin rod of height h, placed as shown in the figure. The beaker height is 3h and its radius h. When the beaker is filled with a liquid up to a height 2h, he can see the lower end of the rod. Then the refractive index of the liquid is


(a) 5/2                                    (b) 5/2

(c) 3/2                               (d) 3/2

(b) The line of sight of the observer remains constant, making an angle of 45° with the normal.


       sin θ=hh2+2h2=15μ=sin 45°sin θ=1/21/5=52


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