(a) An object is placed well outside the principal focus of a convex lens. Draw a ray diagram to show how the image is formed, and say whether the image is real or virtual.
(b) What is the effect on the size and position of the image of moving the object (i) towards the lens, and (ii) away from the lens?

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Solution

(a) When an object is placed well outside the principal focus of a convex lens, the image formed is real and inverted as shown in the figure.

(b)
(i) When an object is moved towards the lens, the size of the image starts increasing. The position of the image starts moving away from the lens and towards infinity (on the right side of the lens) till the object is placed at the focus. When the object is moved closer to the lens, the image is formed behind the object (left side of the lens). This image is virtual, erect and magnified in size.
(ii) When the object is moved away from the lens, the image so formed moves closer to the lens and gets diminished in size.

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