Assertion: lens's length | /r/CapableOf | vary proportional
Facets:
value: to the kinetic energy
type: TRANSITIVE-OBJECT
value: for a magnetostatic lens
type: PURPOSE
Source sentences:
text: So for an electrostatic lens the focal length varies with the second power of the kinetic energy, while for a magnetostatic lens the focal length varies proportional to the kinetic energy.