DrG-Physics · Interference · SQA Higher Physics revision

Higher Physics on coherent light, Young’s slits, and the diffraction grating. Five SQA-style questions fully worked. EXAM + STUDY editions included.

A focused single-topic revision companion on Interference for SQA Higher ‘Particles & Waves’ (the wave half — Volume II — Light). Covers coherence, the path-difference conditions, Young’s double-slit experiment, and the diffraction grating equation.

The DrG-Physics revision companion is not a worksheet. It is a structured exam-thinking guide — built around the way an SQA marker reads your script. Each worked solution leads with the relationship the examiner is looking for, substitutes cleanly, and evaluates with units. Every question carries a marker-aligned command-word tag (CALCULATE · 2 marks · STATE + JUSTIFY) so students learn what kind of answer earns each mark.

WHAT’S INSIDE
• Theory chapter on coherence, path differences, the Young’s double-slit setup, and the diffraction grating, with two diagrams (Young’s slits with fringe pattern, grating with multiple labelled orders)
• Five SQA-style questions covering coherence and path difference, the grating equation for finding wavelength, the maximum order observable, why interference is wave evidence, and the two-wavelength comparison through one grating
• Special focus on the lines-per-mm conversion that catches half the candidates and on the n₀ = 0 zeroth-order maximum
• Examiner’s Note after every question naming the typical pitfall
• Do/Don’t pair to reinforce SQA marking conventions

TWO EDITIONS · ONE DOWNLOAD
• EXAM Edition — clean, concise solutions for printing and exam-style practice
• STUDY Edition — same content plus ‘Why’ reasoning panels before each part

PART OF THE SERIES
One of four topics in ‘Particles & Waves Vol II — Light’. Try PW01 — Standard Model FREE to experience the approach.

Written and produced by Dr Godoy, GTCS-registered Physics teacher, Edinburgh.