Question

An object is to be seen through a simple microscope of focal length 12 cm. Where should the object be placed so as to produce maximum angular magnification? The least distance for clear vision is 25 cm.

Answer 1

Given :

Focal length, f = 12 cm

Least distance of clear vision, d = 25 cm

For maximum angular magnification,

Image distance = Least distance of clear vision

v = d = − 25 cm

The lens formula:

1/v-1/u=1/f

1/u=1/v-1/f

On substituting the values, we get:

1/u=1/-25 -1/12

1/u =-25+12 / 300

=-37/300

u= -300/37

= - 8.1 cm

to produce maximum angular magnification, the object should be placed 8.1 cm away from the lens.

Answer 2

Answer:

8.1 cm from the lens.

For the given simple microscope.

f=12cm and D=25cm

For maximum angular magnification, the image should be produced at least distance of clear vision.

So, v=−D=−25cm

Now,

v

1

−

u

1

=

r

1

⇒

u

1

=

v

1

−

f

1

=

−25

1

−

12

1

=−

300

37

⇒u=−8.1cm

so, the object should be placed 8.1cm away from the lens.