1
Question
An object is placed at a distance of 12 cm from the optical centre of a convex lens of focal length 20 cm, as shown:
Answer the following questions based on the given details.
i. What will happen to the size of the image if we move the object away from the lens?
[1 mark]
An object is placed at a distance of 12 cm from the optical centre of a convex lens of focal length 20 cm, as shown:
Answer the following questions based on the given details.
i. What will happen to the size of the image if we move the object away from the lens?
[1 mark]
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Solution
The correct option is C The size of the image will first increase and then decrease.
As the object is placed at a distance which is less than the focal length, a magnified image is formed on the same side behind the object.
When the object is moved away from the lens, the size of image first increases, as it is highly magnified at the focal length. After that, when we move beyond the focal length between F1 and 2F1, we get a magnified image which is smaller as compared to the image formed when the object was at F1. As we keep moving away, the size of the image keeps on decreasing.
Thus, we can say that as we move away from the lens in the given case, the size of the image will first increase and then decrease.
As the object is placed at a distance which is less than the focal length, a magnified image is formed on the same side behind the object.
When the object is moved away from the lens, the size of image first increases, as it is highly magnified at the focal length. After that, when we move beyond the focal length between F1 and 2F1, we get a magnified image which is smaller as compared to the image formed when the object was at F1. As we keep moving away, the size of the image keeps on decreasing.
Thus, we can say that as we move away from the lens in the given case, the size of the image will first increase and then decrease.
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