There are no rules, for this or for anything else in writing, except coherance.
Some people end a chapter when a particular situation has reached its conclusion, and it's a good spot to put the book down. Others do the same thing, but they try to make something interesting happen at the end to make you want to read on to the next. Some others do a mix of the two and sort of stop the chapter when its beat is over, but while the scene is sort of in mid-step in order to keep the momentum up and going on to the next chapter.
None of these are right or wrong, it's really up to you, and what's good for your story. I'd prefer to do the third one on a strong action-oriented story. But if you're telling a more slow story, like say, in Contact, where it's mostly just science and dialogue for the first 200 pages or so, you're building up momentum much more gradually rather than trying to always grab your reader by his hair and pulling as hard as you can.
Ultimately there's no formula. I've seen great chapters that have been a mere sentence long. I've also seen great chapters that have ran nearly seventy pages without a break. And I've seen a lot of crappy chapters go all over the scale. What matters is the writing itself, and the story.
You're never going to hear about anybody throwing the book in the trash can because they felt the chapter ended too soon, y'know? Boring your reader is always something you should be afraid of, but that too has nothing to do with chapter length. What it has to do with is being a boring writer.
That said, chapters make a good spot for readers to stop reading if they need to, so the more frequent you can have them, the more reader-friendly it will be to those people who're reading before going to bed, who need to wake up for an important meeting the next morning. So if you can avoid 50 page chapters, it would probably be appreciated. But it's not going to be a deal-breaker for any decent reader.