Advantages and disadvantages of using first and second order lines to identify spectra

[dsptl]

I know there are many ways to identify the spectra but,

what are the advantages and disadvantages of using the first and second order lines to identify spectra?

Please Help!

If u don't want give me answer then suggest me some links.

Thanks

 

[dsptl]

any help?

 

[dsptl]

someone help please...only hours left to turn in!