Question

An object $\left(O\right)$ is placed in front of a concave lens of focal length $9.8m$ as shown. Which of the positions best describes the location of the image if the distance between O and the lens is $15.7m$?

• A. Position $A$
• B. Position $B$
• C. Position $C$
• D. Position $D$
• E. Position $E$

Answer 1

The correct option is A Position $A$

Given: $f=-9.8m$ and $u=-15.7m$ ,

From lens formula:

$v=\frac{uf}{u+f}$

$v=\frac{-15.7\times -9.8}{-15.7-9.8}=153.86/-25.5=-6.0m$

Since $v$ is negative therefore image is apparent and formed on the same side of lens.

Now, linear magnification $m=v/u=-6.0/-15.7=+0.38$

As m is positive, it means image is erect. Therefore, image will be formed at A.