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5:35 AM
Folks, say I've got an optical grating. It will disperse light into the spectrum, and it will create several orders.
How is the total light energy distributed between the orders? If I send one order to the detector, how much energy would I miss in the remaining orders?
Say, the incoming light is white, if that simplifies things.
 
 
2 hours later…
8:01 AM
@misk94555 Maybe you should ask that as a question on some StackExchange site, maybe physics.stackexchange.com
 
 
6 hours later…
2:30 PM
@misk94555 That's a very good and fundamental question! There are simple approximations that can be used to calculate that as long as the lines of the grating aren't too small. But to get a very precise answer one needs to either measure it or do a very challenging electromagnetic simulation
In practice one looks it up in a book or uses information from a catalog before ordering it, but it can be calculated.
I think you can ask the question "How do Astronomers estimate the amount of reflected light that goes into each order of a hypothetical diffraction grating if they don't have a specific grating for which they can check the specifications?"
Of course, someone may answer "We don't" or "We just assume it's 10 to 50% and worry about the details later" but it is also possible that someone will show the math.
If nobody else does, then I will :-) so I'd say go ahead and post a question like that here in Astronomy SE. If you need more details after answers are all in, then you can ask a follow-up question in Physics SE.
Or alternatively you can ask first in Physics SE. In principle that would be the better place, but in practice sometimes optics questions get ignored there.
I wish there was an Optics SE specific site!!
 
 
5 hours later…
7:42 PM
John Rennie at the Physics chat had pointed out this article, which describes the sinc function: hyperphysics.phy-astr.gsu.edu/hbase/phyopt/gratint.html
@uhoh What kinds of catalogs might have this [empirical?] information? I've looked for data about higher orders in the grating datasheets(Thor, Edmund, Newport). But they don't seem to mention anything about higher orders.
 

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