Question

the focal length of a converging lens is 20cm .An object is at 60cm from the lens where will the image form???​

Answer 1

Answer:

1/f=1/v-1/u

1/20=1/v-1/60

1/20+1/60=1/v

1/80=1/v

v=80

Answer 2

Answer:

Given:

Object Distance (u) = - 60cm

Focal Length (f₁) = 20cm

To find: Image Distance (v)

From the Lens formula,

1/f = 1/v - 1/u

We get, v = f x u/ f + u

= v = 20 x (-60)/ 20 - 60

= 20 x 60/40 = 30cm

⇒ Image Distance = 30cm

∴ The image is formed in between F₁ and 2F₁.

   Nature of the Image is (a) Real (b) Dimenished (c) Inverted

(ii) Given:

Height of the Object ($h_o$) = 2cm

To find: Height of the Image ($h_i$)

We know that,

= $\frac{h_i}{h_o}$ = $\frac{v}{u}$ ⇒ $\frac{h_i}{2}$ = 30/-60 = 1/-2 ⇒ $\frac{1}{-2}$ ⇒ $h_i$ = -1cm

∴ Height of the Image is 1cm, which is below the principal axis.

⇒ For more Clarification, you can observe the figure in the Attachment.