I don't understand what is in my lecture notes. What equations do I need to attempt this question?
We can't give any assistance unless you can show us some attempt at a solution. Also, just saying you don't understand what's in your lecture notes is way too vague. We need specifics about what equations or statements you don't understand. If your lecture notes or textbook are available online, please give a reference.
Hi, I can't really put my lecture notes on here - they're too long to post and it would identify the university. I've taken a screenshot of the section of the notes where those equations are from. It's a past paper question on the subject of radiaton protection. I don't have a book so any guidance would be valuable.
https://image.ibb.co/eeJgXJ/notes.jpg
There is a formula on the following website, is this along the right lines?