CBSE Class 10 Science 2020 · Paper 31/5/3 · Question 29(b)

(a) From the top of the object, a ray parallel to the principal axis is reflected through F, and a ray striking the pole P is reflected at an equal angle on the other side of the axis. The reflected rays diverge; their dashed extensions behind the mirror meet, and the dashed image A′B′ is drawn there (see the completed diagram). (b) The image is virtual and erect; it is formed behind the mirror, $30$ cm from P; it is enlarged, twice the size of the object. (c) With $f=-30$ cm and $u=-15$ cm, $\frac{1}{v}=\frac{1}{f}-\frac{1}{u}=-\frac{1}{30}+\frac{1}{15}=\frac{1}{30}$, so $v=+30$ cm, and the magnification is $m=-\frac{v}{u}=-\frac{+30}{-15}=+2$.