Question

An object is placed $30cm$ in front of a convex lens of focal length $10cm$. Find out the distance of the image from the lens and its nature? Assume the object distance to be negative.

• A. $-15cm$, Real and Inverted
• B. $+15cm$, Real and Inverted
• C. $-15cm$, Virtual and Erect
• D. $+15cm$, Virtual and Erect

Answer 1

The correct option is B $+15cm$, Real and Inverted

Given:
Object Distance, $u=-30cm$
The focal length of the lens, $f=10cm$
Focal length is positive for convex lens.

Using Len's formula,
$\frac{1}{v}-\frac{1}{u}=\frac{1}{f}$
$\frac{1}{v}+\frac{1}{30}=\frac{1}{10}$
$\frac{1}{v}=\frac{1}{10}-\frac{1}{30}$
$v=+15cm$

So, the distance of the image from the lens is $15cm$. Since, the object is placed beyond the focus, nature of the image is real and inverted.