HOw do you define absorption spectrum?

Question

I read absorption spectrum on wikipedia but I don't understand it, how do you define it?

Answer 1

Below is another source. try it...

http://www.ask.com/web?q=define+absorption+spectrum&search=&qsrc=0&o=0&l=dir
http://theory.uwinnipeg.ca/mod_tech/node152.html

Answer 2

I think learned it in astronomy. The way my teacher talked about it was that, when you have an object that is far away and you cant get a sample of it, and want to know what it is made of, you look at what kind of light it absorbes. For example if the object has hydrogen it may abosorb red light or whatever. so scientists measure what light it absorbes and they see it absorbed red light so they know it has hydrogen. haha i dont think im helping am i? well i tried.