Question

An object is placed at a distance of 15 cm from a concave lens of focal length 20 cm find the position and nature of image..

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Answer 1

Answer:

Explanation:

Solution,

Here, we have

Object distance, u = - 15 cm

Focal length, f = 20 cm

To Find,

Position and nature of the image.

According to the lens formula,

We know that,

1/f = 1/v - 1/u

1/v = 1/f + 1/u

So, putting all the values, we get

1/v = 1/f + 1/u

⇒ 1/v = 1/20 + 1/- 15

⇒ 1/v = 1/20 - 1/15

⇒ 1/v = 3 - 4/60

⇒ 1/v = - 1/60

⇒ v = - 60 cm

Hence, the image distance is 60 cm.

Nature of lens,

Virtual and erect.

Image will form on the same side of lens

Enlarged

Answer 2

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Question :-

⋄ An object is placed at a distance of 15 cm from a concave lens of focal length 20 cm find the position and nature of image..

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❍ Given :-

⋄ Object distance (u) =-15cm

⋄ Focal length (f) = 20 cm

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❍ To Find:-

⋄ Position and Nature of Image.

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❍ Solution :-

By using Lens Formula

1/v-1/u= 1/f

➧ 1/v= 1/f +1/u

➧ 1/v= 1/(20)+1/(-15)

➧ 1/v=1/5(1/4 -1/3)

➧ 1/v= 1/5×-1/12

➧ 1/v=-1/60

➧ v= -60 cm

∴ The image distance is -60cm.

⋄Nature of image ⋄

➠ The image produce by concave lens is virtual, erect.