Question

an object is placed at a distance of 4cm from a concave lens of focal length 12cm. find the position and nature of object

Answer 1

Since the question is incomplete I took some liberty and took an assumption.. Hope the solution helps

Answer 2

The image is located at a distance of 3 cm from the lens in the same side of object. Image is virtual, erect and magnified.

Explanation:

It is given that,

Object distance, u = -4 cm

Focal length of the concave lens, f = -12 cm

Let v is the image distance. Using mirror's formula to find it as :

$\dfrac{1}{f}=\dfrac{1}{v}-\dfrac{1}{u}$

$\dfrac{1}{v}=\dfrac{1}{f}+\dfrac{1}{u}$

$\dfrac{1}{v}=\dfrac{1}{(-12)}+\dfrac{1}{(-4)}$

v = -3 cm

So, the image is located at a distance of 3 cm from the lens in the same side of object. Image is virtual, erect and magnified.

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Lens formula

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