Question

An object of length 2.5 cm is placed at a distance of 1.5 f from a concave mirror where f is the magnitude of the focal length of the mirror. The length of the object is perpendicular to the principal axis. The length of the image is

• A. 5 cm, erect
• B. 10 cm, erect
• C. 15 cm, erect
• D. 5 cm, inverted

Answer 1

The correct option is D 5 cm, inverted

By using $\frac{I}{O}=\frac{f}{f-u}$; where I =?, $O=+2.5cm.f\to -f,u=-1.5f$
$\therefore \frac{I}{+2.5}=\frac{-f}{-f-(-1.5f)}\Rightarrow I=-5cm$.(Negative sign indicates that image is inverted.)