Detectors of radiation

Different types of radiation are detected differently. Radio receivers are electrical circuits tuned to the approprate frequency; visible light can be detected with the eye, with photographic film, photoelectric devices and others; x-rays can be detected with photo film, and so on.

Antennas are devices for gathering more radiation than would be received without them. They range from big dish reflectors for radar, to the pupil of your eye, and telescopes, for visible light, to lengths of wire for low frequency radio waves.