Question

The diagram below shows a lens as a combination of a glass slab and two prisms. 

1. Name the lens formed by the combination.
2. What is the rays the line XX’ called?
3. Complete the ray diagram and show the path of the incident ray AB after passing through the lens.
4. The final emergent ray will either meet XX’ at a point or appear to come from a point on XX’. Label the point as F. What is this point called?

Answer 1

1. The combination forms a convex lens.
2. XX' is known as principal axis.
3. The path of the ray is shown as CD.
4. Emergent ray will meet XX' at a point F. The point F is called principal focus.