Assertion: beam | /r/CapableOf | occur behind rear focal plane
Facets:
value: for a divergent beam
type: PURPOSE
Source sentences:
text: Note that this measurement is valid only when the beam size is measured at the rear focal plane of the lens, i.e. where the focus would lie for a truly collimated beam, and not at the actual focus of the beam, which would occur behind the rear focal plane for a divergent beam.