CBSE Class 10 Science 2017 · Paper 31/1/1 · Question 4

With $u=-30$ cm and $f=+15$ cm, the mirror formula gives $\frac{1}{v}=\frac{1}{15}+\frac{1}{30}=\frac{1}{10}$, so $v=+10$ cm, and $m=-\frac{v}{u}=+\frac{1}{3}$. The four characteristics of the image are: (1) Virtual: it is formed behind the mirror and cannot be obtained on a screen. (2) Erect: $m$ is positive. (3) Diminished: it is one-third the size of the object. (4) Position: 10 cm behind the mirror, between the pole $P$ and the principal focus $F$.