|The Electromagnetic Spectrum|
|AM radio||102m||1 MHz||10−9 eV|
|FM, TV||1 m||100 MHz||10−7 eV|
|Radar||.1m||1000 MHz||10−6 eV|
|Microwaves||10−2m||1010 Hz||10−5 eV|
|Infrared||10−5m||1013 Hz||10−2 eV|
|Visible light||10−7m||1015 Hz||1 eV|
|Ultraviolet||10−8m||1016 Hz||10 eV|
|X-rays||10−10m||1018 Hz||1 keV|
|γ-rays||10−13m||1021 Hz||1 MeV|
The electromagnetic spectrum is the entire range of electromagnetic radiation extending in frequency from zero Hertz to 1023 cycles per second (or Hertz).
Longer wavelengths of electromagnetic radiation such as used in AM radio have lower frequencies (540 to 1600 kHz). FM radio has much shorter wavelengths and higher frequencies (88 to 108 MHz).
Even higher frequencies give as microwave radiation, used in radar and cooking. Still higher is infrared (which can keep food warm from a lamp or heat up your skin from sunlight or fire). Infrared is used in "black light" photography.
Next highest in frequency (and lower in wavelengths) is visible light: red, orange, yellow, green, blue, indigo and violet.
Ultraviolet light can give you a suntan (or burn), and too much of certain UV frequencies can increase one's risk of skin cancer. Some frequencies are blocked by the Earth's ozone layer.
Even higher frequencies include X-rays and gamma rays. Both are known to be hazardous because of their ability to pass through, and cause damage to, flesh and organs.
More colloquially, the spectrum is simply the range of electromagnetic radio frequencies used in the transmission of sound, data and television.