Question

The image of an object formed by a mirror is real, inverted and is of magnification $-1$. If the image is at the distance of $30cm$ from the mirror, where is the object placed? Find the position of the image if the object is now moved $20cm$ towards the mirror. What is the nature of the obtained? Justify your answer with the help of ray diagram.

Answer 1

Formula,

$m=\frac{v}{u}$

$-1=\frac{40}{u}$

$u=-40$

$\frac{1}{f}=\frac{1}{v}+\frac{1}{u}$

$=-\frac{1}{40}-\frac{1}{40}=-\frac{1}{20}$

$\Rightarrow f=-20$

the image of the object is located at the infinity. As, if the object is moved 20cm towards the mirror, then it lies at the focus of the mirror.