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Question: A candle flame 3 *cm* is placed at distance of 3 *m* from a wall. How far from wall must a concave m...

A candle flame 3 cm is placed at distance of 3 m from a wall. How far from wall must a concave mirror be placed in order that it may form an image of flame 9 cm high on the wall

A

225 cm

B

300 cm

C

450 cm

D

650 cm

Answer

450 cm

Explanation

Solution

Let the mirror be placed at a distance x from wall

By using

IO=−vu⇒−9+3=−(−x)−(x−3)\frac { I } { O } = \frac { - v } { u } \Rightarrow \frac { - 9 } { + 3 } = \frac { - ( - x ) } { - ( x - 3 ) } ⇒x=−4.5m=−450 cm\Rightarrow x = - 4.5 m = - 450 \mathrm {~cm}