Question

an object is placed at a distance of 15 cm from a concave mirror. images formed and distance of 10 cm in front of the mirror what is the focal length of mirror

Answer 1

$object \: distance(u) = - 15cm \\ image \: distance(v) = - 10cm \\ focal \: length(f) = to \: be \: find \\ mirror \: formula = > \frac{1}{f} = \frac{1}{u} + \frac{1}{v} \\ \frac{1}{f} = - \frac{1}{15} - \frac{1}{10} \\ \frac{1}{f} = \frac{ - 2 - 3}{30} \\ \frac{1}{f} = - \frac{5}{30} \\ \frac{1}{f} = - \frac{1}{6} \\ f = - 6 \\ therefore \: focal \: length \: = - 6cm$