Question

in what distance should a body be put in front of a concave mirror, knowing that the focal distance is 20cm, for the image would be real and reduced?

Answer 1

For a concave mirror according to image formation table,

If the object is beyond C i.e. center of curvature, the image formed is real and diminished.

Therefore, the object should be placed beyond C of the mirror to get a real and dimnished image.

For a mirror,

c=2f, given that f=20cm

Hence, c=40 cm

Therefore the body should be put slightly beyond a distance of 40cm from the mirror.