Difference between revisions 1695659 and 1695660 on enwikiversity

'''Electromagnetic radiation''' comes in many different types, although the differences between them are quantitative rather than qualitative.  This teaching aid lists the different types that are generally recognised.

Electromagnetic radiation is an Electromagnetic oscillation wave that travels at speed of visible light carries[[Quantum]]'s energy called [[Photon]]

==Electromagnetic oscillation wave==
(contracted; show full)

This is a relatively narrow band, covering a factor of no more than two in wavelength or frequency.  However, it is comparatively well defined.

It has been reported that some people who have had cataracts removed can see shorter wavelengths than other people, because they get replacement lenses in their eyes that are more transparent to these wavelengths than natural lenses.  A well-documented case is the astronomer [http://ehilbert.wso.net/Starlight/deep_sky_wonders.htm Walter Scott Houston].


==Ultraviolet==
* '''Near ultraviolet''': 400-300nm
* '''Middle ultraviolet''': 300-200nm
* '''Extreme or far ultraviolet''': 200-100nm

* '''Vacuum ultraviolet''' is UV with wavelengths shorter than about 150-200nm.  Such wavelengths are strongly absorbed by air, especially oxygen, so are best used in a vacuum.  However, it is possible to use pure nitrogen rather than a vacuum.

'''UVA, UVB, UVC''' are terms used to assess how dangerous the UV is to human skin.

* '''UVA''': 320-400 nm: Not absorbed by ozone layer; fairly harmless		
* '''UVB''': 280-320 nm: Partly absorbed by ozone layer; more dangerous		
* '''UVC''': 100-280 nm: Totally absorbed by ozone layer; most dangerous

Short-wave UV, X-ray and gamma-ray radiation are sometimes lumped together as '''ionising radiation''', because the photons are energetic enough to knock electrons out of atoms, ionising them.  Such radiation is dangerous to living things, because the ionisation can disrupt biochemical processes and even cause cancer.  Alpha and beta particles can also be called ionising radiation.⏎
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==X-rays==
{{main|Radiation/X-rays|X-ray radiation|X-rays}}
These have a wavelength of 0.01 to 10 nm, hence photon energies of 1keV to 1000keV.  They were discovered by Wilhelm Roentgen in 1895.

(contracted; show full)'''Ultraviolet radiation''' was discovered by Johann Wilhelm Ritter in 1801.

There are several terms used.

==External links==
[[Category:Physics]]
[[Category:Radiation]]
[[Category:Resources last modified in August 2016]]