Question

To get a real image of the same size as the object, where should the object be placed in front of a convex lens?

• A. At the principal focus
• B. At a distance twice the focal length
• C. At infinity
• D. Between the optical centre and the principal focus

Hint:

Memorize standard ray diagrams: Object at \(2F\) yields an image at \(2F\) of the same size.

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
The nature, position, and size of an image formed by a convex lens depend on the position of the object relative to the lens.

Step 2: Detailed Explanation:
When an object is placed exactly at a distance of \(2f\) (twice the focal length) from the optical centre of a convex lens, the image is formed on the other side at a distance of \(2f\).
This image is real, inverted, and exactly of the same size as the object.

Step 3: Final Answer:
The object must be placed at a distance twice the focal length.