The following figure represents two biconvex lenses and having focal lengths and , respectively. The distance between and is:
The figure shows: and are mounted coaxially on a common principal axis, with on the left. A ray travelling parallel to the principal axis is incident on from the left, above the axis. After refraction at the ray converges, crosses the principal axis at a point between the two lenses, and goes on to meet below the axis. After refraction at it emerges travelling parallel to the principal axis again.
- A
- B
- C
- D
