CBSE Class 10 Science 2017 · Paper 31/1/3 · Question 16

Nature of the mirror: concave, because the image is formed on a screen, so it is real, and only a concave mirror can form a real image of a real object. Focal length: with $u=-30$ cm and $v=-60$ cm, $\frac{1}{f}=\frac{1}{v}+\frac{1}{u}=-\frac{1}{60}-\frac{1}{30}=-\frac{1}{20}$, so $f=-20$ cm (a focal length of 20 cm). Height of the image: $m=-\frac{v}{u}=-2$, so $h^{\prime }=m\times h=-2\times 2.4=-4.8$ cm; the image is 4.8 cm tall. The image is inverted (the negative sign of $m$ and $h^{\prime }$), as well as real and magnified.