I'd like to express my gratitude to you for creating this video; your explanations have greatly facilitated my understanding. This video is proving invaluable as I prepare for my upcoming board exam in December!
So the RBE is used to compare the biological effects of different types of ionising radiation. It's defined as the ratio of the dose for our reference radiation (e.g. x-rays) to the dose of radiation in question (e.g. alpha particles) that would cause the same biological effect. If the latter requires 'less dose' to get the same 'biological effect' than x-rays, then we say it has a higher RBE (i.e. relative biological effectiveness). Essentially diving the x-ray dose to the alpha particle dose (both at their 50% survival fraction), that is if the alpha particle requires less dose for the same effect as x-rays, you'd be dividing by a smaller number, i.e. results in a larger number overall which is the RBE. Hope that helps!
