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  4. A person 1.6 m tall is standing at the centre between two walls three metre high. What is the minimum size of a plane mirror fixed on the wall in front of him, if he is to see the full height of the wall behind him?

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Q. A person $1.6\, m$ tall is standing at the centre between two walls three metre high. What is the minimum size of a plane mirror fixed on the wall in front of him, if he is to see the full height of the wall behind him?

Ray Optics and Optical Instruments

Solution:

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$\tan \theta=\frac{h_{1}}{d}=\frac{1.6-h_{1}}{d / 2}\,\,\,...(i)$
$\tan \alpha=\frac{h_{2}}{d}=\frac{1.4-h_{2}}{d / 2}\,\,\,...(ii)$
$h_{1}=\frac{3.2}{3}$ and $h_{2}=\frac{2.8}{3}$
$3-h_{1}-h_{2}=1 \,m$