If lenses are sharing a face, a beam coming from the outside is not refracted at the internal inferface.
If a beam is is coming from the inside of one element (e.g. fluorescence), it is refracted at the internal inferface, but not at the outer surface of the other element.
If lenses are sharing a face, a beam coming from the outside is not refracted at the internal inferface. If a beam is is coming from the inside of one element (e.g. fluorescence), it is refracted at the internal inferface, but not at the outer surface of the other element.