Electromagnetic spectrum
The electromagnetic spectrum is the collection of all possible frequencies of electromagnetic waves, which we commonly refer to as light.
| Type of wave | Frequency range | Wavelength Range |
| Radio Waves | 300 GHz to as low as 3 kHz, | 1 millimeter to 100 kilometers |
| Microwaves | (0.3 to 300) GHz | 1 mm to 1 m |
| Infrared | 300 GHZ to 430 THz | |
| Visible Light | (430–790 THz | 390 to 700 nm |
| UV | 750 THz to 30,000 THz | 10 to 400 nm |
| Xray | 30,000 THz to 300,000 THz | 0.001 to 10 nm |
| Gamma | 300,000 THz to 30,000,000,000 THz | 0.000000001 to 0.001 nm |
Electromagnetic waves have many different properties, and one of the most interesting ones is the property of duality. As asserted by the double-slit experiment (one of the experiments that inspired quantum mechanics), electromagnetic waves behave like both particles and waves, depending on the experiment being used to identify it. If an experiment tries to detect light as a particle, it will. If an experiment tries to detect light as a wave, it also will. For example, if we were to make a barrier with two extremely small slits in it, so that light could pass through, then shined a source of light on it, a detector on the other side would detect a series of lines, even in places that were not behind the slit. This can only lead to the conclusion that the detector was detecting an interference pattern. On the other hand, if we shine light onto a polished piece of metal, we find that it generates current. This should only be possible if light is a particle.
One famous equation describing the energy of light is 
, where 
is the energy of the light, 
is Planck's constant and 
is the frequency of the light.
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