Question

A magnifying lens has a focal length of 100 mm .An object is placed at some distance from the lens so that an image is formed at a distance 25 cm in front of the lens. What is the distance between the object and the lens.?
pls answer ​

Answer 1

Answer:

) Step 1:

Given data in the question

focal length (f) = 100 mm

object size (h) = 16 mm

picture distance (v) = 25 cm = 250 mm

Step 2:

Lens formula is given by:

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

f

1

=

v

1

−

u

1

\frac{1}{100} = \frac{1}{250} - \frac{1}{u}

100

1

=

250

1

−

u

1

\frac{1}{u} = \frac{(2-5)}{500}

u

1

=

500

(2−5)

u= -166.67 mm

u= -16.66 cm

Step 3:

The target is 16.66 cm away and in front of that mirror. The picture is 25 cm away and in front of that mirror. So the distance from the source to the image is

25 cm - 16.66 cm = 7.14 cm.

(b) For the picture to be created at infinity the object should be positioned at the center.