rcs equations

I’m looking for rough, rule of thumb equations. Like the one which states that to cut the radar’s range in half, against a certain rcs, one needs to decrease its rcs 16 times. So a simple rule of thumb like that.

What I’m interested is importance of radar wavelength in RCS. like, for every increase of wavelength X, the RCS increases Y. I know it probably isn’t such a straightforward affair, but i’m really looking just for ballpark figures.

Links to respected works stating such rule of thumbs would be most welcome. thank you. 🙂