Question

The object is placed at 10cm from the optical center of the lens having focal length 12cm find the image distance

Answer 1

the image will be formed at a distance of 5.45 cm.

Explanation:

For a lens, the lens formula is given as :

1/f = 1/v - 1/u

given, f = focal length = 12 cm

u = object distance = 10 cm

v = image distance = ?

hence,

1/12 = 1/v - 1/10

=> 1/v = 1/12 + 1/10

=> 1/v = 22/120

=> v = 120/22 = 5.45 cm

Hence the image will be formed at a distance of 5.45 cm.

Answer 2

When calculating the image distance of an object, the lens formula can be used which is

1/f=1/v+1/u

With the focal length and object distance in mind, calculating the image distance is easy with the above formula .

Nevertheless if the magnification produced by the lens is already known , the image distance can as well be calculated by apppying this formula

m= -v/u = hi/ho whereby hi stands for the height of the image while ho stands for thr height of the object.

In this case the suitable formula is the lens formula i.e 1/f=1/v+1/u

v-image distance

u-object distance-10cm

f-focal length-12cm

1/12=1/v+1/10

1/v=1/12-1/10     1/v=-1/60

v=-60

(check working in the attached file)