Question

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A concave lens has focal length of 20 cm. At what distance from the lens a 5 cm tall object be placed so that it forms an image at 15 cm from the lens? Also calculate the size of the image formed.

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Answer 1

Refer the the image

Hope it helps uhh❤️ Dishant~

Answer 2

Answer:

According to the question,

Image distance, v=−15 cm (negative due to convex lens)

Focal length, f=−20 cm

Let the object distance be u.

By lens formula:

v1−u1=f1[4pt]

⇒−15 cm1−u1=−20 cm1[4pt]

⇒u1=20 cm1+−15 cm1[4pt]

⇒u1=60 cm3−4=60 cm−1[4pt]

⇒u=−60 cm

Therefore, object is placed at 60 cm away from the lens, on the same side as image.

Now,

Height of object, h1=5cm

Magnification, m=h1h2=u

Explanation:

Sorry for late answering Dear