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Question
In the following diagram, L1 and L2 are the two convex lense placed at separation equal to the sum of focal lengths of the two lenses. A and B are the two rays of light incident on the lens L1. Complete the path of rays till they emerge out of the lens L2.

What principles have you used in completing the diagram?
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Solution
The complete ray diagram is shown below.

The following two principles have been used in completing the diagram:
(i) A ray of light incident parallels to the principal axis after refraction from the convey lens passes through the focus.
(ii) A ray of light incident on the convex lens through its focus after refraction becomes parallel to the principal axis of the lens.
RELATED QUESTIONS
The diagram below shows a lens as a combination of a glass slab and two prisms.
- Name the lens formed by the combination.
- What is the line XX’ called?
- Complete the path of the incident ray AB after passing through the lens.
- The final emergent ray either meets XX’ at a point or appears to come from a point on XX’. Label it as F. What is this point called?

A ray of light after refraction through a lens emerges parallel to the principal axis of the lens. The incident ray either passes through ______.
Study the diagram shown in Fig. 5.56
where is the object located?

Study the diagram shown in Fig. 5.56
Where is the image formed?

The diagram given below shows the position of an object OA in relation to a converging lens L whose foci are at F1 and F2.

- Draw two rays to locate the position of the image.
- State the position of the image with reference to the lens.
- Describe three characteristics of the image.
- Describe how the distance of the image from the lens and its size change as the object is moved towards F1.
The diagram given below shows the position of an object OA in relation to a converging lens whose foci are at F1 and F2.

Describe three characteristic of the image.
(a) Draw a sketch to show how a lens is able to produce an image of the sun on a paper screen.
(b)(i) Would you regard the rays from the sun as being divergent, parallel or convergent?
(ii) What is the name given to the point where such rays meet after they have passed through the lens?
(iii) How does the image of the sun sometimes burn a paper screen?
The diagram showed a lens as a combination of one glass block and two prisms. Complete the ray diagram and show the part of the incident ray AB after passing through the lens.
(i) Name of the lens formed by the combination.
(ii) What is the line XX’ called?
(iii) Mark the focus F.

Mixture of red + blue + green is passed through a convex lens as shown in the diagram below. State whether the ray passes through a single point or through different points on the principal axis after refraction.

