So, I just started an internship, and I'm worried that I'm asking too many questions. I've been assigned a mentor who has been assigning me projects and helping me learn all the company's technologies and methodologies. However, there's so much new material for me to learn while doing this project that I have a lot of questions. I generally ask questions over instant messages or E-mail (those are the primary modes of communication for my company).

I'm trying to be careful not to ask too many questions: I don't want to come off as annoying or dumb. How many questions is appropriate to ask? Once an hour? More? Less? Keep in mind, my mentor is also a fellow programmer that has his own responsibilities.