linear double refraction of light

For the linear double light refraction:

A The 2 spherical objects act like lenses and the image formed depends on the position of the object relative to the focal length of the objects. A larger real, inverted image forms when the object is between F and 2F of the 1st object. A real, diminished inverted image forms if the object is beyond 2F. A virtual, enlarged and upright image forms when the object is between F and the object. Object on F no image forms. Object on 2F the image is real inverted and the same size as the object. Where F stands for focal length. Because the objects are spherical they have relatively small focal lengths and thus all the above can be observed in one shot.

 

Bonus