Can one get into Ravenshaw University for a B.Sc. with 80%?

Yes, you can get admission to Ravenshaw University. But this may vary depending on the Honours subject you are willing to choose. 

For some subjects, you can land up in the second cutoff list whereas for others you can get called indirectly for the admissions. Choose your honors subject wisely while filling up the form.

80% and above is sufficient enough to get a seat in dept.s with higher intake capacities.

If you are from the general category, there is a good chance of getting a B.Sc. with a PCM major. If you belong to the reserved category, it should hardly be any problem.