A single-topic, no-prep secondary worksheet on binary search for KS4 / GCSE Computer Science revision, cover lessons and homework. Covers what binary search is, why the list must be sorted, tracing binary search, worst-case comparisons, and why it is O(log n) compared with O(n) linear search. Includes a student worksheet and a separate answer key. Mapped to AQA GCSE Computer Science 8525, 3.1 Fundamentals of algorithms — Searching algorithms and Efficiency of algorithms.