Question

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

Answer 1

Answer: 450.00

The object (Candle) should lie between $f$ and $2f$ of concave mirror, in order to get real, magnified and inverted image a wall.
There fore concave mirror should be placed beyond $3m$ so that candle lies in between $f\&2f$.