Electromagnetic spectrum
The electromagnetic spectrum - in short EM spectrum and more precisely called electromagnetic wave spectrum - is the totality of all electromagnetic waves of different wavelengths. The light spectrum, also known as the colour spectrum, is the part of the electromagnetic spectrum that is visible to humans.
The spectrum is divided into different ranges. This division is arbitrary and in the low-energy range is based on the wavelength for historical reasons. In each case, wavelength ranges over several orders of magnitude with similar properties are grouped into categories such as light, radio waves, etc.. A subdivision can also be made according to frequency or according to the energy of the individual photon (see below). For very short wavelengths, corresponding to high quantum energy, a division by energy is common.
Ordered by decreasing frequency and thus increasing wavelength, at the beginning of the spectrum are the short-wave and thus energy-rich gamma rays, whose wavelengths extend into atomic orders of magnitude. At the end are the longest waves, whose wavelengths are many kilometres long.
The conversion of the wavelength λ 
into a frequency 
done with the formula 
. Here 
the speed of light.
· Overview of the electromagnetic spectrum
· 
Overview with visible spectrum in detail
See also
- Frequency band
- Water window
Questions and Answers
Q: What is the electromagnetic spectrum?
A: The electromagnetic spectrum is the range of all possible electromagnetic radiation.
Q: Can electromagnetic radiation be divided into octaves?
A: Yes, electromagnetic radiation can be divided into octaves similar to sound waves.
Q: How many octaves exist in the electromagnetic radiation spectrum?
A: The electromagnetic radiation spectrum can be divided into up to eighty-one octaves.
Q: What are the limits of electromagnetic radiation?
A: The short wavelength limit of electromagnetic radiation is likely to be the Planck length, and the long-wavelength limit is the size of the universe itself.
Q: What is the range of electromagnetic radiation that can commonly exceed the ionization energy of atoms?
A: Electromagnetic radiation shorter in wavelength than about 30 μm has the ability to exceed the ionization energy of atoms.
Q: How is electromagnetic radiation longer than 3mm commonly detected?
A: Electromagnetic radiation longer in wavelength than 3mm is commonly detected by its ability to induce electrical currents.
Q: Why was radiation between the limits of 30 μm and 3mm little used until the 21st century?
A: Radiation between the limits of 30 μm and 3mm was little used until the 21st century because it was difficult to detect.
