Question

At what distance from a concave mirror of focal length 10 cm should an object be placed, so that it's real image is formed 20cm form the mirror ?

Answer 1

Answer:20cm in front of the mirror

Explanation:f=-10cm

v=-20cm

let the distance from a concave mirror be u

1/v+1/u=1/f

=>1/-10+1/20=1/u

=>1/u=1/-20

therefore u=20cm