19.4. The Electromagnetic Spectrum http://www.ck12.org
FIGURE 19.15
The electromagnetic spectrum.produced by various objects, including people and animals. Astronomical instruments make use of every part of the
electromagnetic spectrum. There are radio telescopes, microwave telescopes, infrared telescopes, x-ray telescopes,
gamma ray telescopes and, of course, optical telescopes that detect visible light. Some of these telescopes are located
on Earth and some in outer space, where the atmosphere does not obscure the part of the spectrum detected by the
telescope.
On a more mundane note, microwaves can cause water molecules to oscillate at their resonant frequency and
therefore a microwave oven can heat (cook) any substance containing water.
Figure19.16 shows the same portion of the sky photographed in infrared wavelengths and visible light.