Question

A 2.0cm high object is placed on the principle axis of concave mirror at a distance of 12cm from the pole.If the image is inverted real and 5.5cm high then the focal length of the mirror

Answer 1

$$m=\frac{-5.5}{2}=-2.75$$

$$d_i=(-2.75)12=-33\ cm$$

$$-\frac{1}{33}=\frac{1}{f}-\frac{1}{12}$$

$$f=18.9\ cm$$