Check out this comparison of the depth of field at f/2 on 50, 35, and 9mm lenses on different sensor sizes. Note that this is about coverage and sensor size, not depth of field as related to focal length with the same coverage. If the coverage is the same, the depth of field is the same regardless of focal length—see this explanation and examples at Luminous Lanscape.
Tag: depth of field
Mike Johnston clarifies depth of field vs. depth of focus
They aint the same! Get the poop at The Online Photographer.