Answer to Question #102032 in Optics for UduakObong Charles

Question

an object is placed in front of a converging lens of focal length 20cm, the image is virtual and has a magnification of 2. what is the distance of the object from the lens

Answer 1

We can write the formula of lens as

$\frac{1}{d} - \frac{1}{f} = \frac{1}{F} (1)$

where d is the distance between the object and the lens, f is the distance between the ge imaobject and the lens, F is the focal lenght

The magnification is given by formula

$m=\frac{f}{d} (2)$

In our case, m=2, F=20 cm

We put (2) in (1)

$\frac{1}{d} - \frac{1}{2d} = \frac{1}{F} (3)$

Using (3) we get

d=10 cm

Answer

10 cm