Q12 of 62 Page 186

A student wants to determine the height of a flagpole. He placed a small mirror on the ground so that he can see the reflection of the top of the flagpole. The distance of the mirror from him is 0.5 m and the distance of the flagpole from the mirror is 3 m. If his eyes are 1.5 m above the ground level, then find the height of the flagpole. (The foot of student, mirror and the foot of flagpole lie along a straight line).


Here,


In the above Figure,


DE is the distance of student and mirror.


EG is the distance of mirror and flagpole.


CD is the height of student till its eyes.


FG is the height of flagpole which we need to find.


Now,


In ΔCDE and ΔFGE


∠FEG = ∠CED (by mirror property)


∠CDE = ∠FGE (both perpendicular given)


∴ ΔCDE ∼ ΔFGE


(∵ ΔCDE ∼ ΔFGE)



⇒ FG = 9 m


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