Simply put, it is the entire range of electromagnetic radiation (EMR). Classically EMR is viewed as a self-propagating transverse oscillating wave of magnetic and electric fields, that travel at the speed of light (in a vacuum).
Source: Wikipedia (https://upload.wikimedia.org/wikipedia/commons/3/35/Onde_electromagnetique.svg)
They are also described Quantum Mechanically in terms of massless elementary particles known as photons (quanta of EM waves), which are particles that behave both like waves and particles and are effected by gravity. EM waves are characterized by either wavelength or frequency, and this is used to organize them in the range of the spectrum. Below is an image outlining wavelength from shortest to longest: Gamma Ray, X-Ray, Ultraviolet, Visible, Infrared, Microwave and Radio.
Source: NASA (http://imagine.gsfc.nasa.gov/Images/science/EM_spectrum_compare_level1_lg.jpg)
Wavelength is inversely proportional to the wave frequency and energy. EMs with long wavelengths, say Radio waves have lower frequency and lower energy levels. Short wavelengths can be significantly smaller then atoms themselves, while long wavelengths are limited only to the size of our universe! This is one reason why UV rays can be harmful to humans; the higher energy levels of UV in respect to visible light can break down DNA, causing permanent damage to cells.
Why is this relevant?
As it turns out EM waves interact with matter in an interesting manner and this interaction determines what the absorption spectra of atoms will be. Atoms absorb specific frequency of EMR, and to an observer they appear as dark bands in the spectrum, these bands correspond to allowed energy levels within atoms. In reality these bands show that these specific frequencies are scattered in all direction. Conversely the opposite is an emission spectrum, where atoms emit specific frequencies. The image below is the hydrogen absorption spectrum, where the absorption bands are 410nm, 434nm 486nm and 656nm respectively, in essence this is the “finger print” of hydrogen!
Source: The University of Texas at Austin (https://ch301.cm.utexas.edu/svg/H-absorption-spectrum.svg)
The types of electromagnetic radiation by wavelength as mentioned above are broad generalization and there are no set boundaries. But there are some distinctions
- Gamma Ray: The most energetic of the types, it’s usually associated with anything nuclear yet it has many medical uses and security, from PET scans to VACIS to authenticate cargo in a truck.
- X-Ray: You guessed it, this is how doctors see if you have a broken bone. These are highly energetic, and its uses range from Medical CT scans to when you go through airport security.
- Ultraviolet: The violet you cannot see with your eyes, but can be quite harmful to your skin due to its energy levels. Bees can see UV and see flowers differently then we do. Uses can range from using UV as a sterilizer to clean water, to using fluorescent dyes to prevent counter fitting.
- Visible: The wavelength you are used to seeing on a daily basis. From violet, to green to red.
- Infrared: If you have remote control you have definitely been exposed to infrared, the invisible beam that turns your channels. It is called infrared because it’s below the red visible wavelength. Lots of practical uses come from this type, from night vision cameras to hot spot detection uses thermal gear.
- Microwave: You likely have a microwave at home to heat your food, and you guessed it, it uses microwaves. But its heavily used in telecommunications, from Satellites in space, to your GSM signal on your smart phone.
- Radio Wave: The AM/FM radio you may listen on the way to work uses radio waves. But these types of waves have multiple uses, from Radars to detect planes to Ground Penetrating Radar (GPR) that can be used to map water cavities underground.
This is pertinent to Skytech Solutions as these natural realities allows us to determine what type of equipment to use on our Rotary/Fixed-Wing UAVs, when we can use them and what type of data our clients can expect to receive. It allows us to see heat damage on flare stacks, determine plant health, detect moisture on roof tops, see subsurface anomalies and even penetrate the ground, something conventional cameras cannot do.