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What can you recall?
define / describe / state / calculate
Recall and explain
(a) Define the angle of refraction. (b) Describe what happens to a ray of light that passes from air into glass along the normal. (c) In an experiment, a pupil traces a ray of light through a triangular glass prism on paper. State whether the ray that leaves is parallel to the ray that went in, and give the reason. (d) Supplement. A ray in air enters a block of clear plastic of refractive index 1.42. The angle of refraction is 24°. Calculate the angle of incidence.
define: give the precise meaning. describe: give the features or what happens. state: give a concise answer. calculate: work out the answer from the data.
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Scope and sources
Cambridge IGCSE Physics 0625 · 2026–2028 v2 · Original learning materials.
The normal, the angle of incidence and the angle of refraction (3.2.2.1); refraction by a rectangular and a semicircular glass block (3.2.2.2); the passage of light through a transparent material, at a boundary between two mediums (3.2.2.3); the critical angle (3.2.2.4); internal reflection and total internal reflection, with experimental and everyday examples (3.2.2.5); Supplement: refractive index as the ratio of the speeds of light (3.2.2.6), n = sin i ÷ sin r (3.2.2.7), n = 1 ÷ sin c (3.2.2.8) and optical fibres, particularly in telecommunications (3.2.2.9). Refraction of water waves is in Waves in a ripple tank, lenses in Lenses and images, and dispersion in Light and the electromagnetic spectrum.
Apparatus, amounts and times in the experiment are illustrative. Real practical work follows a teacher-approved safety method.
Official Cambridge syllabus