Where do you place the object in front of a convex lens to get a real and equal size image of an object? (a) At the principal focus of the lens, (b) At twice the focal length (c) At infinity (d) Between the optical centre of the lens and the principal focus

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Chapter 9

NCERT

Class 10

Science

Solutions

3. Where do you place the object in front of a convex lens to get a real and equal size image of an object?

Question:

Where do you place the object in front of a convex lens to get a real and equal size image of an object?

(a) At the principal focus of the lens,

(b) At twice the focal length

(c) At infinity

(d) Between the optical centre of the lens and the principal focus

Answer:

(b) At twice the focal length

Explanation: The image is formed at infinity when the object is placed (b) at twice the focal length of the convex lens. The image formed will be real, inverted, and of same size.

If we place the object (a) at the principal focus of the lens, the image formed will be real, inverted, and magnified. It will form at infinity.
If we place the object (c) at infinity, the image formed will be real, inverted, and diminished. It will form at the focus.
If we place the object (d) between the optical centre of the lens and the principal focus, the image formed will be virtual, erect, and enlarged. It will form between the optical centre of the lens and its principal focus and on the same side of the object.

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(All Q's of this Chapter solved)

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