Physics Paper 1 · P4 · Lesson 4.8
Start with one half, then read a clear decay graph.
Half-life is the time for the number of undecayed nuclei of an isotope to halve. It can also be measured from the time for the source’s activity or corrected count rate to halve.
Grey circles are changed nuclei, not vanished atoms. This model uses exact halves; real small samples fluctuate.
No timer. Read the explanation after each answer.
Daily 5 · Core exam practice · Higher Tier questions · A4 revision sheet
Lessons 4.1–4.10 cover the core. Lesson 4.11 is Higher Tier only. Daily 5 practises core facts. Answer positions are shuffled on each new attempt; lessons begin with very simple questions.
AQA Combined Science Trilogy specification · 6.4.2.3 · Core. Original notes, questions and diagrams. Experimental numbers are illustrative.
Photos: Geiger counter by Boffy b, enhanced by Marco Plassio; caesium source by Wusel007, enhanced by Partynia, both CC BY-SA 3.0. Rutherford at McGill, 1905, unknown photographer / Wellcome Images, public domain. Photos displayed without cropping or other alterations.
