5.4.137 - Background radiation

Understand that there is background radiation and how to take appropriate account of it in calculations.

Use - background radiation to connect the rule to the data and decision in the question.

This matters because - background radiation determines what can be inferred or chosen; begin with the stated conditions and keep the conclusion tied to the evidence.

Example: apply - background radiation to one small, clearly defined case, show the key step or comparison, and explain the result in words.

Boundary: - Background radiation is not a universal recommendation. Check the syllabus scope, assumptions, units and the limits of the evidence before generalising.