Question

1. Copy the diagram and show the formation of the image of the object AB.
2. What is the name given to Х?
3. What is the kind of lens?
4. State characteristics of the image.

Answer 1

(a) Two rays from A locate the image:

1. The ray from A parallel to the axis spreads out after the lens. Its backward extension (dashed) passes through X.
2. The ray from A through the optical centre O goes straight through without bending.

These two lines meet at A′, giving the image A′B′ between X and O on the same side as the object. 

(b) X is the first principal focus (F₁) of the lens.

(c) Concave lens (diverging lens). The parallel ray spreads out after refraction, as if it came from X.

(d) The image is:

1. Virtual
2. Erect
3. Diminished
4. Formed between the focus X and the optical centre O, on the same side as the object