Question

The image distance of an object placed 10 cm in front of a thin lens of focal length +5 cm is at :

• A. 6.5 cm
• B. 8.0 cm
• C. 9.5 cm
• D. 10.0 cm

Answer 1

Answer: (D)

10.0 cm

Given:

The object distance $u=-10cm$

The focal length of the lens $f=+5cm$

From the lens formula,

$\frac{1}{f}=\frac{1}{v}-\frac{1}{u}$

$\Rightarrow \frac{1}{5}=\frac{1}{v}-\frac{1}{-10}$

$\Rightarrow \frac{1}{v}=\frac{1}{5}-\frac{1}{10}=\frac{1}{10}$

$\therefore v=10cm$

Thus, the distance of the image from the lens is $v=10cm$ and it is on the other side of the lens.