What should be the minimum height of man "Y" (as shown in figure ) so that he may see image of S in mirror?

120cm

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140cm

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100cm

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130cm

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Solution

The correct option is B 140cm
In $Δ A B S \frac{A B}{A S} = t a n θ \Rightarrow \frac{20}{20} = t a n θ = 1 θ = 45^{\circ}$
$θ = 45^{\circ} I n Δ B C D \frac{D C}{B C} = t a n 45^{\circ} \Rightarrow D C = B C \Rightarrow D C = 120 c m = y Height of the person is y+20cm = 120 + 20 = 140 c m H e i g h t = 140 c m$

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What should be the minimum height of man "Y" (as shown in figure ) so that he may see image of S in mirror?

The correct option is B 140cmIn Δ ABSABAS=tan θ ⇒ 2020=tan θ=1θ=45∘ θ=45∘In Δ BCDDCBC=tan 45∘⇒DC=BC⇒ DC=120cm=yHeight of the person is y+20cm=120+20=140cmHeight=140cm