WordNet sense 1 (the state of the environment in which a situation exists):

background, setting

WordNet sense 2 (an area in which something acts or operates or has power or control:):

compass, orbit, range, reach, ambit

WordNet sense 3 (a magnifier of images of distant objects):

telescope

WordNet sense 4 (electronic equipment that provides visual images of varying electrical quantities):

oscilloscope, CRO, cathode-ray oscilloscope