Optical radiation, visible, UV, and infrared


This diagram is at the limit of what should be attempted in a single «pa» Parsing Analysis diagram. As always, please remember:

The aim of the snippet analysis here is to define some regions in the electromagnetic spectrum that we can associate with different kinds of telescopes. Wikipedia notes:

Which is just as well, because the Wikipedia pages are all over the place when it comes to defining what does and does not count as "optical" infrared and what does and does not count as near infrared.

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We already have a block RegionEM; it has been given value properties lMin and lMax (where the 'l' stands for lambda), and we can use the existing ValueType wavelength[nanometre] with Unit nanometre from the ISO-80000 ModelLibrary. These value properties can be redefined to carry fixed values in concrete specialisations of RegionEM, which can then in turn be assigned to different specialisations of the block RadiationEM.

Recall this problematic snippet?

Describing 1mm infrared as "optical" is almost certainly wrong. Dedicated submillimeter telescopes that operate over 300 μm use technology that is not in any sense regular optical. Nevertheless, for now the value range 100 nm to 1,000,000 nm indicated is naively used for block OpticalRange.

Compare with:

That snippet can be safely used to glean range values for RegionVisible and «infrared» RegionIR. However we already know that not all of the infrared spectrum can be treated as «optical», so we need a more restrictive «optical» «infrared» RegionOpticalIR. The following give an indication where the line can be drawn (or better said pragmatically cherry-picked):

Wikipedia has a table on the bands used in infrared astronomy, and although it describes the "near infrared" as going up to the M band, the K band offers itself as a good (relatively arbitrary) cut-off point:

Beyond the K-band it indicates telescope support as only 'Most dedicated infrared telescopes and some optical telescopes'. So we'll take 2.4 μm (2400 nm) as the cut-off point for «optical» «infrared».

This stated range for UV actually spills over the visible range a bit, but is taken for «uv» RegionUV:

The limit of the wavelength is then redefined as 100 nm in «optical» «uv» RegionOpticalUV.

These different regions are then assigned as the type of region in specialisations of RadiationEM. For example, in «visual» VisualLight (which extends «optical» Light) it is redefined as region:RegionVisible[1].

The UV and infrared cases are trickier. The block «uv» RadiationUV does not extend Light; however the more specific «uv» «optical» LightUV extends both RadiationUV and Light, and has a dual redefinition region:RegionOpticalUV.

Similarly, «infrared» «optical» LightIR extends both «infrared» RadiationIR and «optical» Light, and has a dual redefinition region:RegionOpticalIR[1].

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