Assertion: focal ratio | /r/HasProperty | calculated
Facets:
value: by dividing its focal length
type: MANNER
Source sentences:
text: The focal ratio of a telescope is calculated by dividing its focal length by its aperture size.
text: It can be calculated by dividing the focal length of the telescope by its aperture.
text: The focal ratio is calculated by dividing the focal length by the objective diameter.