By drawing ray diagrams, discuss the characteristics of the image formed by a convex lens when the object is:
(a) between the optical centre and the focus.
(b) at the focus.
(c) at $2 F_{1}$ .
(d) at infinity.
[5 MARKS]

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Solution

part(i): 2 Marks
part(ii): 1 Mark
part(iii): 1 Mark
part(iv): 1 Mark

(a) The image formed when the object AB is between the optical centre (O) and focus (F) is shown in Fig. 5.29

Characteristics of the image formed: The image is on the same side as the object. It is virtual, erect or upright and magnified.

(b) The image formed when the object AB is at the focus is shown in Fig. 5.30.

Characteristics of the image formed: The image is at infinity on the other side of the lens. It is real, inverted and highly magnified.

(c) The image formed when the object AB is at $2 F_{1}$ is shown in Fig. 5.31.

Characteristics of the image formed: The image is formed at $2 F_{2}$ on the other side of the lens. It is real, inverted and of the same size as the object.

(d) The image formed when the object AB is at infinity is shown in Fig. 5.32. The light rays from any point of such object can be treated as parallel.

Characteristics of the image formed: The image is formed at the focus on the other side of the lens. It is real, inverted and highly diminished.

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Draw ray diagrams to represent the nature, position and relative size of the image formed by a convex lens for the object placed : (a) at $2 F_{1}$ , (b) between $F_{1}$ and the optical centre O of the lens. Which of the above two cases shows the use of the convex lens as a magnifying glass ? Give reasons for your choice.

Draw ray diagram showing the image formation by a convex lens when an object is placed at infinity.

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By drawing ray diagrams, discuss the characteristics of the image formed by a convex lens when the object is: (a) between the optical centre and the focus. (b) at the focus. (c) at 2F1. (d) at infinity. [5 MARKS]

By drawing ray diagrams, discuss the characteristics of the image formed by a convex lens when the object is:
(a) between the optical centre and the focus.
(b) at the focus.
(c) at $2 F_{1}$ .
(d) at infinity.
[5 MARKS]