In one phenomenon named for these objects, geodesics are bent around a massive object, yielding results like a four-pointed Einstein cross surrounding a massive galaxy.
In particle accelerators, a magnetic analogue of these devices consists of a series of quadrupole magnets. When these devices are dispersive, they are said to suffer from a chromatic defect. In one phenomenon named for these objects, geodesics are bent around a massive object, yielding results like a four-pointed Einstein cross surrounding a massive galaxy. The power of these devices is measured in units of inverse length and is conventionally given in diopters. An approximation named for a "thin" one can be used to compute their focal lengths. Non-ideal ones suffer from coma and other optical aberrations. For 10 points, name these objects that refract light.
In particle accelerators, a magnetic analogue of these devices consists of a series of quadrupole magnets.
lens [prompt on "focuser" or "collimator"]