Question

At what distance from a concave mirror of focal length 10cm should an object 2 cm long the place in order to get an erect image 6 CM tall?

Answer 1

Answer: -6.7 cm

Explanation:

Focal length of concave mirror f() = -10 cm

Height of the object (ho) = 2 cm

Height of the image (hi) = 6 cm

To find: Distance of object from mirror=?

So Magnification (m) = hi/ho = 6/2 = 3 (erect image)

m = -v/u

3 = -v/u

v = -3u

Mirror formula: 1/v + 1/u = 1/f

1/(-3u) + 1/u = 1/(-10)

u = -20/3 = -6.7 cm

So At -6.7cm distance from a concave mirror of focal length 10cm should an object 2cm long be placed in order to get an erect image 6cm tall.