CBSE Class 10 Science 2020 · Paper 31/C/1 · Question 22

(a) The object should be placed between the centre of curvature C and the principal focus F. In the ray diagram, a ray from the top of the object parallel to the principal axis passes through F after reflection, and a ray through F is reflected parallel to the axis; the two reflected rays meet beyond C, below the axis, so the image A′B′ is real, inverted and enlarged (for example, $f=-10$ cm and $u=-15$ cm give $v=-30$ cm and $m=-2$). (b) With the object at C, the image is also formed at C, real, inverted and of the same size, so the magnification is $m=-1$.