Question

an object 4cm high is placed at a distance of 6cm in front of a concave mirror of focal length 12cm. find the position of the image​

Answer 1

for the concave mirror

object distance (u) = -6 cm

focal length (f) = -12 cm

we know that, by mirror formula–

$\frac{1}{v} + \frac{1}{u} = \frac{1}{f} \\ \frac{1}{v} = \frac{1}{f} - \frac{1}{u} = \frac{u - f}{uf} \\ v = \frac{uf}{u - f} = \frac{( - 6)( - 12)}{ - 6 - ( - 12)} \\ v = \frac{72}{ - 6 + 12} = \frac{72}{6} \\ v = + 12 \: cm$

Hence, the image is formed 12 cm behind the mirror.