Contents
Independent final check
Explain without the key
define / describe / calculate
Final check
(a) Define the angle of incidence. (b) A pupil shows refraction with two transparent blocks on paper: a rectangular glass block and a triangular glass prism. Describe how she records the direction of the ray that leaves each block, and how that ray compares with the ray that went in, for each shape. (c) Supplement. Define refractive index in terms of the speed of light. (d) Supplement. A ray in air meets a transparent crystal with an angle of incidence of 43°. The angle of refraction is 26°. Calculate the refractive index of the crystal.
define: give the precise meaning. describe: give the features or what happens. 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