## Overview This topic covers the spontaneous nature of nuclear decay and the nature of alpha, beta and gamma radiation. It introduces the concept of half-life, activity and decay constant. Learners study the exponential decay law in both graphical and algebraic form. ## Working Scientifically There are opportunities within this topic for learners to plot and interpret graphs; to process and analyse data using appropriate mathematical skills; to safely and correctly use a range of practical equipment and materials; to make and record observations; to use ionising radiation, including detectors. ## Mathematical Skills There are a number of opportunities for the development of mathematical skills in this unit. These include recognising and making use of appropriate units in calculations; recognising and using expressions in decimal and standard form; using an appropriate number of significant figures; finding arithmetic means; understanding simple probability; making order of magnitude calculations; changing the subject of an equation including non-linear equations; solving algebraic equations, including quadratic equations, using logarithms in relation to quantities that range over several orders of magnitude; plotting two variables from experimental or other data; sketching relationships which are modelled by: x y e  = ; applying the concepts underlying calculus (but without requiring the explicit use of derivatives or integrals) by solving equations involving rates of change, for example x x t   = −  using a graphical method or spreadsheet modelling. ## How Science Works There are opportunities within this topic for learners to use appropriate methodology, including ICT, to answer scientific questions and to solve scientific problems; to evaluate methodology, evidence and data, and resolve conflicting evidence to consider ethical issues in the treatment of humans and the environment, to evaluate the ways in which society uses science to inform decision making. ### Learners should be able to demonstrate and apply their knowledge and understanding of: (a) the spontaneous nature of nuclear decay; the nature of α, β and γ radiation, and equations to represent the nuclear transformations using the 𝐴 𝑍 X notation (b) different methods used to distinguish between α, β and γ radiation and the connections between the nature, penetration and range for ionising particles (c) how to make allowance for background radiation in experimental measurements (d) the concept of the half-life, T½ (e) the definition of the activity, A, and the Becquerel (f) the decay constant, λ, and the equation A = λ N (g) the exponential law of decay in graphical and algebraic form, t N N eo − = and t A A eo − = or 2 o x N N = and 2 o x A A = where x is the number of half-lives elapsed – not necessarily an integer (h) the derivation and use of 1 2 ln 2 T  = [[Specified Practical Work]] - Investigation of radioactive decay – a dice analogy - Investigation of the variation of intensity of gamma radiation with distance