Regarding the effectiveness of Botox for frown lines, can I definitely see results after just one injection?

I used to have a habit of furrowing my brow in various situations, especially when I was deep in thought. As I get older, the wrinkles between my eyebrows have become so deep that it makes me look very old and unsophisticated.

So I'm thinking about getting Botox for my frown lines, but I'm wondering if the wrinkles will dramatically disappear after just one injection, or if I need several sessions for them to gradually fade or smooth out.

Can I see a definite effect on frown lines with just one Botox injection?