Assertion: camera lens's length | /r/HasProperty | positive
Facets:
value: for a diverging lens
type: PURPOSE
value: for a concave mirror
type: PURPOSE
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: For a diverging lens (for example a concave lens), the focal length is negative, and is the distance to the point from which a collimated beam appears to be diverging after passing through the lens.
text: For a converging lens (for example a convex lens), the focal length is positive, and is the distance at which a beam of collimated light will be focused to a single spot.
text: The focal length is positive for a concave mirror, and negative for a convex mirror.