Scientific research paper – how broad should the introduction be? My research answered a very specific question. But the hypothesis I was testing will also likely have very broad application. I want to make sure to convey that importance in my paper. Is the first line of the introduction an acceptable place to do that? 

I am thinking the first line of the introduction might be something like:


  For decades our knowledge of myTopic has been insufficient to answer questions like A, B, and C. I considered scenario C₁ to test my hypothesis, which now shown to be correct in this case, will likely play a key role in answering these other questions going forward. Some background on scenario C₁ is...


Or should the introduction only mention background info which is directly relevant to the scenario I actually investigated? And then I can suggest the larger importance of this discovery elsewhere in the paper?
The answer to your question entirely depends on your field and the venue to which you will submit your paper. Software Engineering papers, for example, tend to have much longer and broader introductions than Math papers. Papers at smaller and more focused conferences and journals have shorter and more focused introductions that those at broad venues, since they address a more specific readership.