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QJEEM20Phb14c: JEE Main 2020 Physics - Class 12 JEEM20Phb14c Solution: An observer can see through a small hole on the side of a jar…

An observer can see through a small hole on the side of a jar (radius 15 cm) at a point at height of 15 cm from the bottom (see figure). The hole is at a height of 45 cm. When the jar is filled with a liquid up to a height of 30 cm the same observer can see the edge at the bottom of the jar. If the refractive index of the liquid is N/100, where N is an integer, the value of N is _____. JEE Main 2020 (Online) 3rd September Morning Slot Physics - Geometrical Optics Question 146 English

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JEE Main 2020 (Online) 3rd September Morning Slot Physics - Geometrical Optics Question 146 English Explanation

tan r = 1530{{15} \over {30}} = 12{1 \over 2}

sin r = 15{1 \over {\sqrt 5 }}

1sin 45o = μ\mu sin r

⇒\Rightarrow 12=μ(15){1 \over {\sqrt 2 }} = \mu \left( {{1 \over {\sqrt 5 }}} \right)

⇒\Rightarrow μ\mu = 52\sqrt {{5 \over 2}} = 1.58

μ=N100\mu = {N \over {100}} = 1.58

⇒\Rightarrow N = 158

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