Assertion: lens's length | /r/HasProperty | positive
Facets:
value: for converging lenses
type: TRANSITIVE-OBJECT
Source sentences:
text: The focal length f is positive for converging lenses, and negative for diverging lenses.
text: The focal lengths of this type of lens are negative, this can be worked out mathematically by assigning a negative radii of curvature to a concave lens surface.
text: The focal length f is positive for converging lenses, and negative for diverging lenses.