Hi Ashok,
I might add that how to properly measure risk is one of my very favorite topics. In fact, I wrote my masters thesis on this very subject. It sounds as if it is a pet topic of yours, too?! If so, I would love to hear more about your work here.
In short, standard deviation and beta are not descriptors of risk, in my opinion. They are statistical measures that describe variation and slope in curvilinear geometry and linear geometry, nothing more.
With smiles,
Jason