The compound microscope
This instrument employs two lenses of short focal length arranged as shown in Fig. 24.21. The first of these, called the objective, produces an enlarged, real, inverted image 11 of a small object O.
The image II then acts as an object for the eye lens, which gives a virtual, image 12 which is still further enlarged. This is the image which is seen by the eye.
It should be noticed that the thin rays drawn without arrows in the diagram are only the necessary construction rays to locate the position of the image 12, The actual rays from the object by which the eye sees the tip of the image 12 are the thicker arrowed rays.