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 principle 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

Answer: (D)

5 cm, inverted

Answer 2

By using $\frac { I } { O } = \frac { f } { f - u }$; where I = ? , O = + 2.5 cm. $f \rightarrow - f$, u = – 1.5 f

$\therefore$ $\frac { I } { + 2.5 } = \frac { - f } { - f - ( - 1.5 f ) }$

$I = - 5 \mathrm {~cm}$ (Negative sign indicates that image is inverted.)